Anyone Running just Regular rotella? (15w-40)

k5robnp · **Joined:** Tue May 28, 2013 10:10 am **Posts:** 47

Just wondering if anyone is running just regular shell rotella 15w-40. I have been running t6 the whole time but am very good about keeping to the exact mileage of each oil change. I dont really see any negative effects of running just regular rotella and just changing it more often. I figure better oil pressure will help these engines live longer. I could see it might have a slight negative effect on gas mileage but other than that why not?? The other reason is I have a bunch of other diesel vehicles that use this oil and it would be much nicer to not have to go get different stuff just for the jeep. Its an 05 liberty btw.

thermorex · **Posted:** Fri Jun 20, 2014 10:00 am

Nu As in theory both are 40 weight oils, it seems that T6 is a better oil vs T nonsynthetic. This is the datasheet I found online for both:

T6: http://www.epc.shell.com/Docs/GPCDOC_Local_TDS_United_States_Shell_Rotella_T6_5W-40_(CJ-4)_(en-US)_TDS.pdf
T: http://www.epc.shell.com/Docs/GPCDOC_Local_TDS_United_States_Shell_Rotella_T_Triple_Protection_15W-40_(CJ-4)_(en-US)_TDS.pdf

What I understand from those specs is that the T6 is more fluid at both operating temperature 14.2 vs 15.5 (at 100 deg Celsius) and at 40 degrees Celsius (87 vs 120). so, in theory, the turbo and all oil passages will get better lubrication/flow while the engine warms up as oil is thinner (even if the pressure is not as high, which I really doubt it would be noticeable in between those 2 oils - it is only natural that a thick oil to create more pressure, but the point of an oil is to create lubrication, which is achieved through flow, not pressure, when the oil is too thick it wont go through filter, thus will be sent back to the sump). If the crd is driven for long distances, and once started up, it will be left idling till the oil reaches 200-ish degrees, I think either oil would be fine, the only big difference between the 2 Shell seems to be when the engine is cold, the non synthetic oil seems to be to thick IMO.

Considering the data sheets, it seems that T6 is one of the best oils for diesel, even better than Mobil1 5w40 TDT (14.5 at 100 celsius and 97.9 at 40 celsius), side of highly debated Mobil1 0W40, which in theory is the best for crd engine, based on the datasheet.

So, my personal preference: 1 - Mobil1 0w40, 2 - Shell Rotella T6 5w40, 3 - Mobil1 5w40 TDT, 4- other 40 weight oils

Edit: after I install an oil temp and oil pressure gauge, I'll try even a thinner oil, such as 10w30 or even 5w30, and monitor the pressure and temps.

k5robnp · **Joined:** Tue May 28, 2013 10:10 am **Posts:** 47

Thanks so much for the reply. So when warm they are almost the same viscosity. I have to believe that the passages in the turbo etc are large enough to accommodate the thicker oil when cold. What determines which oil is good for the engine? What is it mostly based on? I would have to believe that a thicker oil would create a better cushion for the the bearings and increase the pressure curve on each bearing and help the overall life. Sorry for asking dumb questions. ...

On another note, this engine seems to have quite a bit of blow by and I personally would like to try to reduce that. Thicker oil is the only way I can think of without having to rebuild the engine with better ring gaps/tolerances to the cylinder walls.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

This same engine in the export market lists 15W-40 as an acceptable oil, CG rating and higher.

thermorex · **Posted:** Fri Jun 20, 2014 1:49 pm

Now I know Keith is not a fan of Mobil1 0w40, lol, and I do not intend to create any argument with him or others, the oil topic is in general a very hot one as each has particular believes and preferences to defend. I try to think things as logical as possible.

In general, most engine wear is at cold start up. This is because the oil is too thick at lower temperatures versus "hot" operating temperatures the engine was designed to run, and oil can't flow through all the passages as well as when is hot. This is why we all want thinner oils at cold. Automakers design engines that should operate under normal conditions, and those normal conditions are at about 212 degrees. This is why anybody sane will recommend warming up the engine, no matter what oil you have in it. When the engine is idling (under no load), there is almost no stress in the moving parts, so a not "perfect" lubrication won't hurt as much as if the engine will be under load at lower temperatures. So, in theory an oil that has the viscosity of let's say 14 at hot and 14 at cold would be ideal. This is impossible due to the properties the oils have, and in this example the T6 oil has the viscosity of 87 at 40 celsius (versus 14 at 100 celsius). As engine warms up over 100 celsius (especially racing conditions or heavy towing - where oil can reach 300degrees but the water is still under 200 range - the heat transfer between engine and cooling fluid is not instant), the oil will also get thinner, this resulting in less oil pressure but more flow (this is pure physics). So (and this is just a guess from my side), at 300F degrees the T6 could have somewhere at 4 or 5 viscosity (versus 14 at 100 celsius), this resulting in less oil pressure but more flow. Flow is what is keeping the engine parts lubricated, not pressure, but in the same time pressure is important since with no pressure there is no flow. I have not found any information on how much oil pressure is in general needed for a particular engine so that would be considered "safe". This is why I will install an oil temp and pressure gauge and start some tests. Every engine is different, but at least in theory, an engine that is not abused under race conditions (so we can make a safe assumption that the oil temp will never go over 220F degrees), a thinner oil would be much better, especially at startup, since it's viscosity at cold will be better (thinner). Just keep in mind that neither oil that is sold on the markets meets the required manufacturer specs for running at hot (ex - Crd needs a 40 weight oil, which has a 13.5 -14 viscosity at 100 celsius, but the thinnest oil on the market in 40 weight - the 0w40 from Mobil1 - has the viscosity of 75 at 40 celsius- which does not mean it is 5 times thicker at 40 than at 100 celsius, those are just some numbers that define viscosity - probably invented to make things harder to understand for us). This means that no matter what oil you put in your car it will not meet the requirements of the engine's manufacturer when cold (will be too thick at cold). There are just better oils for cold start or worse, but not a perfect one, this is why is very important to do a basic engine warmup, to help the oil temp reach a higher temperature that is closer to the intended manufacturer flow specs for the engine.

And yes, there are people using 15w40 nonsynthetic oils and are very meticulous in oil changes and engine warmup, those engines will obviously last much longer than the average Joe's that uses 0w40 full synthetic and changes it when he remembers... And this being said, one of the main differences between synthetic and nonsynthetic, even both are petroleum products, synthetics have a chemically changed formula, which makes them more stable under heat variations. Mineral oil degrade much easier. Synthetic oils are by definition thinner, and the most noticeable difference starts in sub-zero temperature, where you can actually start your car with a synthetic oil but can't with mineral oil. All oils should be changed right after winter, when weather warms up, due to waxes that are generated due to repeated hot-very cold conditions, which waxes are not caught by the filters all the time (so the tendency for the oil is to thicken up). So, other than the price, it is always better to use synthetic oils bottomline.

So, unfortunately the question what oil is best for your engine does not have an easy answer. In theory you need to go as thin as possible with the oil while you are still keeping a decent amount of pressure, enough to create the flow that moves the oil throughout the engine. How much is the pressure? I have no idea, the old school racing mechanics say that you should get 10 PSI per every 1000 rpm, but how that applies to our engine, I can't answer. I am not sure if some specific information is available in one of the FSMs for CRD, but I'd be definitely interested to find it out.

In other words, I think you'll be fine with the nonsynthetic Shell, as long as you do often and regular oil changes, warm it up before you touch the acceleration pedal, and maybe switch to some synthetic for the winter to be easier on startup, if you live in the north.

k5robnp · **Joined:** Tue May 28, 2013 10:10 am **Posts:** 47

such great info. Thanks so much. Yeah its the wifes car and she usually drives mostly long distances. We are very good about letting our vehicles warm up a fair amount even in the summer before we ever touch the gas. I had a lengthy conversation yesterday with a very experienced race engine builder who is also a good friend about the differences between oils, weather its synthetic or just a different brand. I guess this is more for engines with non roller lifters but he was saying that most synthetic oils lack the cushioning effect. He explained it as putting some in the palm of your hand and slapping it with your finger. The regular oil would mostly stay in your hand but the synthetic would just scatter. Again thank you guys for the really detailed and knowledgeable responses. I have also heard about the 10psi for every 1000 rpm addage. Not sure if that holds true still but seems like it would. I will certainly switch back to synthetic in the winter time but we live here in North carolina so its mostly hot and doesnt get all that cold very often.

papaindigo · **Posted:** Fri Jun 20, 2014 4:25 pm

For what it's worth in the endless what oil to use debate:
1. be gentle on the engine when 1st started. Yes I know some still believe in warm up in the driveway but that leaves the entire drive line behind the engine cold as a stone. Better - crank up, wait until oil pressure shows, drive gently until coolant temp begins to rise and you will be fine.
2. be religious about turbo cool down. Nothing cooks oil better than leaving some of it sitting in a scalding hot turbo
3. use quality oil filters and reasonable oil change intervals. Sorry to those who like long intervals, absent routine oil analysis, I'm sticking with no more than ca. 6,000 miles between changes.
4. whatever oil you use it must be diesel rated.

Beyond that I don't see much point in the 0 vs 5 vs 10 vs 15W-40 debate. I use Rotella T-6 Full Synthetic 5W-40 which can be found for $19-22 per gallon. Rotella 15W-40 seems to run $13-15 per gallon. The CRD uses 7 qts with an oversize filter so that's about $38.50 vs. $26.25 per oil change respectively based on the higher end of the price range. For a cost differential of $12.25 per 6,000 miles or so who cares.

That said if you have a variety of vehicles all of which are happy with the Rotella 15W-40 which you buy in bulk and you want the convenience of using 1 type of oil across your "fleet" then it should do fine in your CRD as long as you pay attention to the above notes. Probably would be fine even in the winter in NC especially if you use the block heat when temps get down to the 20s and pay attention to not pushing the engine until coolant temp starts to come up.

PS the VM motor engine oil passages per geordi, who has seen the inside, are tiny.

k5robnp · **Joined:** Tue May 28, 2013 10:10 am **Posts:** 47

yes I am a firm believer and know that driving easy until the thermostat kicks in and the tranny heats up WILL make your vehicle last longer. We are very easy on the vehicles, even in the summer, until they completely warm up. Looks like itll be changing to 15w-40 like the rest of the fleet. Thanks again. I will probably reduce the change interval to 4500-5000 instead of the 6250 were using now on the synthetic.

DOC4444 · **Posted:** Fri Jun 20, 2014 9:26 pm

According to Keith, the oil temp in the turbo in the VM 2.8 reaches 275 degrees F. Petroleum oil based, non-synthetic oil just does not tolerate that for long.

I simply would never use pure petroleum oil under these conditions. With a GDE tune, so little soot builds up that 10,000 mile oil changes are just fine, so there is little cost savings by using dino and 5000 mile intervals.

DOC

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

DOC4444 wrote:

According to Keith, the oil temp in the turbo in the VM 2.8 reaches 275 degrees F. Petroleum oil based, non-synthetic oil just does not tolerate that for long.

I simply would never use pure petroleum oil under these conditions. With a GDE tune, so little soot builds up that 10,000 mile oil changes are just fine, so there is little cost savings by using dino and 5000 mile intervals.

DOC

No oil will last very long at 275 F. That is the max limit for this engine under intermittent operating conditions. 99% of the time it is nowhere close to this temperature. We have many customers that do extended oil change intervals of 10-15k, but they all perform regular oil analysis. On my personal CRD, it is changed every 8000 miles.

CIMARRON13 · **Posted:** Sat Jun 21, 2014 8:08 pm

I run the T6 in everything I own including my lawn mowers. I did switch for awhile to the 15-40 in my Land Cruiser, when it was still gas powered, because it helped slow down the oil leaks.

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

I run 15w40 in summer months and 5w40 in winter months. I do a 30 second idle warmup and then I have a 1/2 mile coast downhill before I actually put a load on the cold engine. 137k miles and engine runs fine except for a MAF code every other month.

mass-hole · **Posted:** Mon Jun 23, 2014 12:34 pm

Drewd wrote:

I run 15w40 in summer months and 5w40 in winter months. I do a 30 second idle warmup and then I have a 1/2 mile coast downhill before I actually put a load on the cold engine. 137k miles and engine runs fine except for a MAF code every other month.

The reason that I don't do this is that the 40 weight oils should be approximately the same viscosity etc at operating temperature which is still much higher than air temps during the summer, so there will be no effect there. Where there will be difference is a cold start. Since the viscosities are ~10x as much at cold start, you are likely going to a.) cause the bypass valve to open on your oil filter possibly letting any crud that's settled in your oil pan flow right through it, and b.) open the pressure relief valve on the oil pump. The relief valve is set to a static pressure, a fluid of higher viscosity will reach this pressure sooner than a lower viscosity fluid since it has more resistance to being forced through the engine. That means less volume will be allowed to flow through the engine with a higher viscosity given that you open the pressure relief valve.

Also, using a higher weight oil because it sticks to the top end of the motor better when you shut it off is also BS. the engine stays hot for a very long time, and if you ever change your oil with a hot motor you know it flows like water. Whether its 15W or 5W its going to drain just is quickly.

mass-hole · **Posted:** Mon Jun 23, 2014 12:44 pm

thermorex wrote:

Now I know Keith is not a fan of Mobil1 0w40, lol, and I do not intend to create any argument with him or others, the oil topic is in general a very hot one as each has particular believes and preferences to defend. I try to think things as logical as possible.

In general, most engine wear is at cold start up. This is because the oil is too thick at lower temperatures versus "hot" operating temperatures the engine was designed to run, and oil can't flow through all the passages as well as when is hot. This is why we all want thinner oils at cold. Automakers design engines that should operate under normal conditions, and those normal conditions are at about 212 degrees. This is why anybody sane will recommend warming up the engine, no matter what oil you have in it. When the engine is idling (under no load), there is almost no stress in the moving parts, so a not "perfect" lubrication won't hurt as much as if the engine will be under load at lower temperatures. So, in theory an oil that has the viscosity of let's say 14 at hot and 14 at cold would be ideal. This is impossible due to the properties the oils have, and in this example the T6 oil has the viscosity of 87 at 40 celsius (versus 14 at 100 celsius). As engine warms up over 100 celsius (especially racing conditions or heavy towing - where oil can reach 300degrees but the water is still under 200 range - the heat transfer between engine and cooling fluid is not instant), the oil will also get thinner, this resulting in less oil pressure but more flow (this is pure physics). So (and this is just a guess from my side), at 300F degrees the T6 could have somewhere at 4 or 5 viscosity (versus 14 at 100 celsius), this resulting in less oil pressure but more flow. Flow is what is keeping the engine parts lubricated, not pressure, but in the same time pressure is important since with no pressure there is no flow. I have not found any information on how much oil pressure is in general needed for a particular engine so that would be considered "safe". This is why I will install an oil temp and pressure gauge and start some tests. Every engine is different, but at least in theory, an engine that is not abused under race conditions (so we can make a safe assumption that the oil temp will never go over 220F degrees), a thinner oil would be much better, especially at startup, since it's viscosity at cold will be better (thinner). Just keep in mind that neither oil that is sold on the markets meets the required manufacturer specs for running at hot (ex - Crd needs a 40 weight oil, which has a 13.5 -14 viscosity at 100 celsius, but the thinnest oil on the market in 40 weight - the 0w40 from Mobil1 - has the viscosity of 75 at 40 celsius- which does not mean it is 5 times thicker at 40 than at 100 celsius, those are just some numbers that define viscosity - probably invented to make things harder to understand for us). This means that no matter what oil you put in your car it will not meet the requirements of the engine's manufacturer when cold (will be too thick at cold). There are just better oils for cold start or worse, but not a perfect one, this is why is very important to do a basic engine warmup, to help the oil temp reach a higher temperature that is closer to the intended manufacturer flow specs for the engine.

And yes, there are people using 15w40 nonsynthetic oils and are very meticulous in oil changes and engine warmup, those engines will obviously last much longer than the average Joe's that uses 0w40 full synthetic and changes it when he remembers... And this being said, one of the main differences between synthetic and nonsynthetic, even both are petroleum products, synthetics have a chemically changed formula, which makes them more stable under heat variations. Mineral oil degrade much easier. Synthetic oils are by definition thinner, and the most noticeable difference starts in sub-zero temperature, where you can actually start your car with a synthetic oil but can't with mineral oil. All oils should be changed right after winter, when weather warms up, due to waxes that are generated due to repeated hot-very cold conditions, which waxes are not caught by the filters all the time (so the tendency for the oil is to thicken up). So, other than the price, it is always better to use synthetic oils bottomline.

So, unfortunately the question what oil is best for your engine does not have an easy answer. In theory you need to go as thin as possible with the oil while you are still keeping a decent amount of pressure, enough to create the flow that moves the oil throughout the engine. How much is the pressure? I have no idea, the old school racing mechanics say that you should get 10 PSI per every 1000 rpm, but how that applies to our engine, I can't answer. I am not sure if some specific information is available in one of the FSMs for CRD, but I'd be definitely interested to find it out.

In other words, I think you'll be fine with the nonsynthetic Shell, as long as you do often and regular oil changes, warm it up before you touch the acceleration pedal, and maybe switch to some synthetic for the winter to be easier on startup, if you live in the north.

It would be nice to hear from people with oil pressure gauges what pressure they see at cold start idle and if it plateaus from the pressure relief valve opening at a certain RPM. Like i said in my previous post, which goes along with what you said, a 5W oil will flow easier than a 15W when cold, and given that the oil pump should push the same volume regardless of oil type, a 5w will allow higher RPM before it goes into pressure relief. Where that occurs i am not sure.

thermorex · **Posted:** Mon Jun 23, 2014 2:27 pm

mass-hole wrote:

thermorex wrote:

Now I know Keith is not a fan of Mobil1 0w40, lol, and I do not intend to create any argument with him or others, the oil topic is in general a very hot one as each has particular believes and preferences to defend. I try to think things as logical as possible.

In general, most engine wear is at cold start up. This is because the oil is too thick at lower temperatures versus "hot" operating temperatures the engine was designed to run, and oil can't flow through all the passages as well as when is hot. This is why we all want thinner oils at cold. Automakers design engines that should operate under normal conditions, and those normal conditions are at about 212 degrees. This is why anybody sane will recommend warming up the engine, no matter what oil you have in it. When the engine is idling (under no load), there is almost no stress in the moving parts, so a not "perfect" lubrication won't hurt as much as if the engine will be under load at lower temperatures. So, in theory an oil that has the viscosity of let's say 14 at hot and 14 at cold would be ideal. This is impossible due to the properties the oils have, and in this example the T6 oil has the viscosity of 87 at 40 celsius (versus 14 at 100 celsius). As engine warms up over 100 celsius (especially racing conditions or heavy towing - where oil can reach 300degrees but the water is still under 200 range - the heat transfer between engine and cooling fluid is not instant), the oil will also get thinner, this resulting in less oil pressure but more flow (this is pure physics). So (and this is just a guess from my side), at 300F degrees the T6 could have somewhere at 4 or 5 viscosity (versus 14 at 100 celsius), this resulting in less oil pressure but more flow. Flow is what is keeping the engine parts lubricated, not pressure, but in the same time pressure is important since with no pressure there is no flow. I have not found any information on how much oil pressure is in general needed for a particular engine so that would be considered "safe". This is why I will install an oil temp and pressure gauge and start some tests. Every engine is different, but at least in theory, an engine that is not abused under race conditions (so we can make a safe assumption that the oil temp will never go over 220F degrees), a thinner oil would be much better, especially at startup, since it's viscosity at cold will be better (thinner). Just keep in mind that neither oil that is sold on the markets meets the required manufacturer specs for running at hot (ex - Crd needs a 40 weight oil, which has a 13.5 -14 viscosity at 100 celsius, but the thinnest oil on the market in 40 weight - the 0w40 from Mobil1 - has the viscosity of 75 at 40 celsius- which does not mean it is 5 times thicker at 40 than at 100 celsius, those are just some numbers that define viscosity - probably invented to make things harder to understand for us). This means that no matter what oil you put in your car it will not meet the requirements of the engine's manufacturer when cold (will be too thick at cold). There are just better oils for cold start or worse, but not a perfect one, this is why is very important to do a basic engine warmup, to help the oil temp reach a higher temperature that is closer to the intended manufacturer flow specs for the engine.

And yes, there are people using 15w40 nonsynthetic oils and are very meticulous in oil changes and engine warmup, those engines will obviously last much longer than the average Joe's that uses 0w40 full synthetic and changes it when he remembers... And this being said, one of the main differences between synthetic and nonsynthetic, even both are petroleum products, synthetics have a chemically changed formula, which makes them more stable under heat variations. Mineral oil degrade much easier. Synthetic oils are by definition thinner, and the most noticeable difference starts in sub-zero temperature, where you can actually start your car with a synthetic oil but can't with mineral oil. All oils should be changed right after winter, when weather warms up, due to waxes that are generated due to repeated hot-very cold conditions, which waxes are not caught by the filters all the time (so the tendency for the oil is to thicken up). So, other than the price, it is always better to use synthetic oils bottomline.

So, unfortunately the question what oil is best for your engine does not have an easy answer. In theory you need to go as thin as possible with the oil while you are still keeping a decent amount of pressure, enough to create the flow that moves the oil throughout the engine. How much is the pressure? I have no idea, the old school racing mechanics say that you should get 10 PSI per every 1000 rpm, but how that applies to our engine, I can't answer. I am not sure if some specific information is available in one of the FSMs for CRD, but I'd be definitely interested to find it out.

In other words, I think you'll be fine with the nonsynthetic Shell, as long as you do often and regular oil changes, warm it up before you touch the acceleration pedal, and maybe switch to some synthetic for the winter to be easier on startup, if you live in the north.

It would be nice to hear from people with oil pressure gauges what pressure they see at cold start idle and if it plateaus from the pressure relief valve opening at a certain RPM. Like i said in my previous post, which goes along with what you said, a 5W oil will flow easier than a 15W when cold, and given that the oil pump should push the same volume regardless of oil type, a 5w will allow higher RPM before it goes into pressure relief. Where that occurs i am not sure.

Totally agree, I plan on adding a temp and pressure gauge for oil very soon, since I want to see what the behavior of a thinner oil in operating temperatures will be, especially if the oil has diesel certifications, I plan on going with a 10w30 or 5w30 synthetic on cold North winters and maybe increase the oil change to 3 k-ish miles. It takes forever for crd to warm up at idle in the winter versus a gasser, and when I finally reach the operating temp while driving, I have to turn off soon since I get to destination.

thermorex · **Posted:** Mon Jun 23, 2014 2:41 pm

mass-hole wrote:

thermorex wrote:

Now I know Keith is not a fan of Mobil1 0w40, lol, and I do not intend to create any argument with him or others, the oil topic is in general a very hot one as each has particular believes and preferences to defend. I try to think things as logical as possible.

In general, most engine wear is at cold start up. This is because the oil is too thick at lower temperatures versus "hot" operating temperatures the engine was designed to run, and oil can't flow through all the passages as well as when is hot. This is why we all want thinner oils at cold. Automakers design engines that should operate under normal conditions, and those normal conditions are at about 212 degrees. This is why anybody sane will recommend warming up the engine, no matter what oil you have in it. When the engine is idling (under no load), there is almost no stress in the moving parts, so a not "perfect" lubrication won't hurt as much as if the engine will be under load at lower temperatures. So, in theory an oil that has the viscosity of let's say 14 at hot and 14 at cold would be ideal. This is impossible due to the properties the oils have, and in this example the T6 oil has the viscosity of 87 at 40 celsius (versus 14 at 100 celsius). As engine warms up over 100 celsius (especially racing conditions or heavy towing - where oil can reach 300degrees but the water is still under 200 range - the heat transfer between engine and cooling fluid is not instant), the oil will also get thinner, this resulting in less oil pressure but more flow (this is pure physics). So (and this is just a guess from my side), at 300F degrees the T6 could have somewhere at 4 or 5 viscosity (versus 14 at 100 celsius), this resulting in less oil pressure but more flow. Flow is what is keeping the engine parts lubricated, not pressure, but in the same time pressure is important since with no pressure there is no flow. I have not found any information on how much oil pressure is in general needed for a particular engine so that would be considered "safe". This is why I will install an oil temp and pressure gauge and start some tests. Every engine is different, but at least in theory, an engine that is not abused under race conditions (so we can make a safe assumption that the oil temp will never go over 220F degrees), a thinner oil would be much better, especially at startup, since it's viscosity at cold will be better (thinner). Just keep in mind that neither oil that is sold on the markets meets the required manufacturer specs for running at hot (ex - Crd needs a 40 weight oil, which has a 13.5 -14 viscosity at 100 celsius, but the thinnest oil on the market in 40 weight - the 0w40 from Mobil1 - has the viscosity of 75 at 40 celsius- which does not mean it is 5 times thicker at 40 than at 100 celsius, those are just some numbers that define viscosity - probably invented to make things harder to understand for us). This means that no matter what oil you put in your car it will not meet the requirements of the engine's manufacturer when cold (will be too thick at cold). There are just better oils for cold start or worse, but not a perfect one, this is why is very important to do a basic engine warmup, to help the oil temp reach a higher temperature that is closer to the intended manufacturer flow specs for the engine.

And yes, there are people using 15w40 nonsynthetic oils and are very meticulous in oil changes and engine warmup, those engines will obviously last much longer than the average Joe's that uses 0w40 full synthetic and changes it when he remembers... And this being said, one of the main differences between synthetic and nonsynthetic, even both are petroleum products, synthetics have a chemically changed formula, which makes them more stable under heat variations. Mineral oil degrade much easier. Synthetic oils are by definition thinner, and the most noticeable difference starts in sub-zero temperature, where you can actually start your car with a synthetic oil but can't with mineral oil. All oils should be changed right after winter, when weather warms up, due to waxes that are generated due to repeated hot-very cold conditions, which waxes are not caught by the filters all the time (so the tendency for the oil is to thicken up). So, other than the price, it is always better to use synthetic oils bottomline.

So, unfortunately the question what oil is best for your engine does not have an easy answer. In theory you need to go as thin as possible with the oil while you are still keeping a decent amount of pressure, enough to create the flow that moves the oil throughout the engine. How much is the pressure? I have no idea, the old school racing mechanics say that you should get 10 PSI per every 1000 rpm, but how that applies to our engine, I can't answer. I am not sure if some specific information is available in one of the FSMs for CRD, but I'd be definitely interested to find it out.

In other words, I think you'll be fine with the nonsynthetic Shell, as long as you do often and regular oil changes, warm it up before you touch the acceleration pedal, and maybe switch to some synthetic for the winter to be easier on startup, if you live in the north.

It would be nice to hear from people with oil pressure gauges what pressure they see at cold start idle and if it plateaus from the pressure relief valve opening at a certain RPM. Like i said in my previous post, which goes along with what you said, a 5W oil will flow easier than a 15W when cold, and given that the oil pump should push the same volume regardless of oil type, a 5w will allow higher RPM before it goes into pressure relief. Where that occurs i am not sure.

+1 to this, even though I think that in Drewd's case, since he is in Texas, he may be OK with a 15w40, if he idles couple minutes more, so oil will warm up a bit and reach a reasonable viscosity, with religious oil changes he shouldn't have sludge, but I one would use synthetic though, as some said, it's not worth the hassle since the cost is only slightly bigger, unless there is just a convenience in stocking one type of oil. What sucks is that there is no easy to find documentation to find out what amount of flow is when oil is let's say at 60 degrees (for a particular oil) and what is the maximum viscosity the crd "likes". I think in our cases, with a newer generation of turbo diesels, a minimum viscosity for oil is also a must, due to higher compression and stress on the engine components, but what is the safe limit, I have no clue either...

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

I use 15w40 in summer months because I'm concerned about the valve train and in my believe a thicker oil will help postpone the inevitable. I also switched because SirSam told me that is what he used in his CRD and I respect his knowledge and experience.

I guess I'm a rebel. You should see the sh*t storm I started on a F150 forum when I shared that I use 5w40 in my ecoboost motor instead of 5w30.

thermorex · **Posted:** Thu Jun 26, 2014 5:47 am

Drewd wrote:

I use 15w40 in summer months because I'm concerned about the valve train and in my believe a thicker oil will help postpone the inevitable. I also switched because SirSam told me that is what he used in his CRD and I respect his knowledge and experience.

I guess I'm a rebel. You should see the sh*t storm I started on a F150 forum when I shared that I use 5w40 in my ecoboost motor instead of 5w30.

Let's see about using a 0w30 in crd, lol...

The easiest way to find out if thicker oil stays on the valve is to do an oil change from 15w to 5 or 0w and listen to the engine when starting up. But since when you run the engine it usually gets to the operating temperature, when you turn off, the 15w40 is at the same thickness as a 0w40 when warm, at least in theory, so it will drain as fast.

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

First oil interval with delo 400 15-40, now. It's also CI-4+, not the CJ-4 crap. All our diesels run 15-40, now I just stock one oil. I have a 55 gallon drum and am gonna get another. EPA is about to ruin engine oils due to mileage standards - friction modifiers and such. I'll do UOA at end of 7000 interval and post.

mikey1273 · **Posted:** Thu Jun 26, 2014 8:32 am

I been using T6 5w40 since I got my CRD in august 2009. It was the most recommended oil and easiest for me to buy locally for a good price. Wall-Mart, tractor supply and all the local auto parts stores have it. Mobile one 5w40 is not as easy to find where I am but not difficult. 0w40 is much more illusive and hard to locate.

I change my oil at about 6,250 miles more or less and send a sample to Blackstone labs yearly. Blackstone says my engine is always wearing well and showing less wear the last 2 tests. They say I can safely extend my oil changes to 8,000 miles but I'm hesitant to do so. .
not going to start or join in on any doo doo storm here..... I do what I do and it seems to be good, so until proven wrong I will do it. I agree with not using non synthetic oil due to the high temps the turbo creates

Anyone Running just Regular rotella? (15w-40)

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