Differental lube

kj75 · **Posted:** Thu Apr 14, 2016 3:44 pm

Just wanting to know if it's OK to use 85w-140 mineral Differental lube front and back.
Every major lube manufacturer recommended Synthetic 80w-140 front and back for whatever reason.
I am located in Australia and we don't get temperatures below 10celsius.
I will also be towing an offroading on weekends.

I read numerous posts and lots of people going back to mineral lube.

Any information will be appreciated.

KJ75

thermorex · **Posted:** Thu Apr 14, 2016 4:36 pm

I think that's the best oil and I also use it. It's thick, so your mileage may be by .5 gal less, but overall, use it, all serious offroaders I know use it. I have Lucas mineral 85w 140 in mine, best there is.

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 292

thermorex wrote:

I think that's the best oil and I also use it. It's thick, so your mileage may be by .5 gal less, but overall, use it, all serious offroaders I know use it. I have Lucas mineral 85w 140 in mine, best there is.

Not Mobil1 Synthetic?

tjkj2002 · **Posted:** Thu Apr 14, 2016 9:54 pm

taroo wrote:

thermorex wrote:

I think that's the best oil and I also use it. It's thick, so your mileage may be by .5 gal less, but overall, use it, all serious offroaders I know use it. I have Lucas mineral 85w 140 in mine, best there is.

Not Mobil1 Synthetic?

The best gear oil for your diffs is not synthetic.

kj75 · **Posted:** Thu Apr 14, 2016 11:44 pm

This is an interesting topic, regarding mineral vs synthetic for the use of gear lubes.
I fully understood mineral vs synthetic in the use of engines, but who would have thought synthetic is recommended for differentials.

From what I have gathered so far mineral would be fine to use and in fact it is what a lot of members use.
I spent a whole day searching for lube recommendation from different companies in Australia (Shell, Penrite, Gulf Western, Valvoline, Castrol etc....), and every single one of them recommended Synthetic 80W-140 front and rear. I guess the reasons synthetic is recommended is the better cold weather flow and also providing better fuel economy.

It turns out my wife works 2 blocks away from Gulf Western Warehouse in Clontarf (north Brisbane) and the 4L ULTRA CLEAR GEAR OIL DIFF LUBE LS 80W140 is only $29.79. This is cheaper than the mineral stuff from Super Cheap / Repco which is at least $40.

I will go with the full synthetic Gulf Western purely because it's cheaper than the mineral I buy from retail stores, and will most likely provide better efficiency.

http://www.gulfwestern.com.au/product/u ... ls-80w140/

KJ75

tjkj2002 · **Posted:** Fri Apr 15, 2016 7:02 am

kj75 wrote:

This is an interesting topic, regarding mineral vs synthetic for the use of gear lubes.
I fully understood mineral vs synthetic in the use of engines, but who would have thought synthetic is recommended for differentials.

From what I have gathered so far mineral would be fine to use and in fact it is what a lot of members use.
I spent a whole day searching for lube recommendation from different companies in Australia (Shell, Penrite, Gulf Western, Valvoline, Castrol etc....), and every single one of them recommended Synthetic 80W-140 front and rear. I guess the reasons synthetic is recommended is the better cold weather flow and also providing better fuel economy.

It turns out my wife works 2 blocks away from Gulf Western Warehouse in Clontarf (north Brisbane) and the 4L ULTRA CLEAR GEAR OIL DIFF LUBE LS 80W140 is only $29.79. This is cheaper than the mineral stuff from Super Cheap / Repco which is at least $40.

I will go with the full synthetic Gulf Western purely because it's cheaper than the mineral I buy from retail stores, and will most likely provide better efficiency.

http://www.gulfwestern.com.au/product/u ... ls-80w140/

KJ75

In a splash oil system(your differentials) synthetic oil is not a good choice and does not transfer heat correctly.What makes synthetic better in a pressure oiled system(engine and trans with a actual pump) makes it bad in a non-pressure oil system like diffs.

Take 2 identical vehicles and have 1 with 85w-140 non-syn gear oil and the other with synthetic gear oil.Drive the same distance in 100 degree+ heat.The vehicle with non-syn gear oil diff will be much hotter then the synthetic one because the of heat transfer but then pull the diff covers off and measure the ring gear temp and you will find the temps are much lower on the non-syn gear oil run gears.

But hey if you want that extra 0.1 mpg go for it,your vehicle.

2 high end offroad diff builders here in the States only recommend 85w-140 non-syn gear oil,from experience it's the better.

thermorex · **Posted:** Fri Apr 15, 2016 2:59 pm

taroo wrote:

thermorex wrote:

I think that's the best oil and I also use it. It's thick, so your mileage may be by .5 gal less, but overall, use it, all serious offroaders I know use it. I have Lucas mineral 85w 140 in mine, best there is.

Not Mobil1 Synthetic?

I use mineral per many recommendations, including Tj's. Also, many axle shops recommend mineral (including G2 if I remember correctly), especially 85w140. Other than a very slight mileage decrease, especially in your case with temp not lower than 10C, it is great, including no leaks through axle seals and better lubrication for gears.

Synthetic Diff oil is a gimmick for paying more and getting a bit better mileage. But if you go offroad, why would you trade better for mileage?

WWDiesel · **Posted:** Fri Apr 15, 2016 4:18 pm

X2 on the Lucas mineral 85w 140, it is very good stuff!!!

G.O.A.T. · **Joined:** Wed Jan 27, 2016 1:11 am **Posts:** 149

I agree with TJKJ I run costal Dino oil. Been running it for years, never have any problems

Sent from my SM-N900P using Tapatalk

kj75 · **Posted:** Tue Apr 19, 2016 1:47 am

Finally got around doing the front and rear diffs, as the old lube has done over 32000km (it was still nice and clean like honey).

Ended up using Synthetic 85W-140 as I got it cheap from lube outlet in Australia.
Jeep is nice and quiet and no leaks observed.
According to the Jeep manual, it is recommended to change diff fluid every 20000km, but I might let the synthetic go a bit longer.

tjkj2002 · **Posted:** Tue Apr 19, 2016 4:30 am

kj75 wrote:

Finally got around doing the front and rear diffs, as the old lube has done over 32000km (it was still nice and clean like honey).

Ended up using Synthetic 85W-140 as I got it cheap from lube outlet in Australia.
Jeep is nice and quiet and no leaks observed.
According to the Jeep manual, it is recommended to change diff fluid every 20000km, but I might let the synthetic go a bit longer.

You actually need to change synthetic gear oil much sooner.

kj75 · **Posted:** Tue Apr 19, 2016 8:37 am

I thought synthetic oils took longer to break down, am I wrong ?
The oil previously used was also synthetic, and looked very nice and clean (although the Jeep never did any offroad).

What would be a good interval to change synthetic diff oil, considering the manual states 20000km when used to tow or offroad ?

tjkj2002 · **Posted:** Tue Apr 19, 2016 1:28 pm

kj75 wrote:

I thought synthetic oils took longer to break down, am I wrong ?
The oil previously used was also synthetic, and looked very nice and clean (although the Jeep never did any offroad).

What would be a good interval to change synthetic diff oil, considering the manual states 20000km when used to tow or offroad ?

Follow the manual since synthetic came from the factory for MPG reasons and why it's shorter intervals.

Synthetic gear oil does not do a good job of protection in diffs and why it generally looks better then dino gear oil after some time.The dino gear oil is actually suspending junk and transferring heat.

tcoilburner · **Posted:** Tue Apr 19, 2016 6:36 pm

I work for a GM dealership. GM actually recommended switching to a synthetic 75w90 gear oil to cut down on warranty repairs on there HD trucks back in 2001. They left the factory with 80w90 mineral oil. If mineral oil is better, than they should not have told the dealer to change the oil on them to save the company warranty costs.

thermorex · **Posted:** Tue Apr 19, 2016 6:40 pm

tcoilburner wrote:

I work for a GM dealership. GM actually recommended switching to a synthetic 75w90 gear oil to cut down on warranty repairs on there HD trucks back in 2001. They left the factory with 80w90 mineral oil. If mineral oil is better, than they should not have told the dealer to change the oil on them to save the company warranty costs.

I'm not contradicting what gm said, but every single offroader I've talked to uses mineral oil. Maybe jeep diffs are different than gm, I doubt, but who knows... Do you have a reason why they did that exactly, what went bad for gm that they say synthetic is better? I can understand some brands may be low quality, but in general, that Lucas 85w140 is the best Diff oil I know of, side limited slip diffs synthetic oils that have friction modifier in it.

tjkj2002 · **Posted:** Tue Apr 19, 2016 8:11 pm

tcoilburner wrote:

I work for a GM dealership. GM actually recommended switching to a synthetic 75w90 gear oil to cut down on warranty repairs on there HD trucks back in 2001. They left the factory with 80w90 mineral oil. If mineral oil is better, than they should not have told the dealer to change the oil on them to save the company warranty costs.

Simple switch to 85w140 non-synthetic would have been a better choice for HD vehicles.

Go to TrueHi9.com and then click on "oiling system",what do they mention 3 times? These center sections see much,much more abuse then most HD pickups ever will while turning 40"+ tires.

tcoilburner · **Posted:** Tue Apr 19, 2016 8:13 pm

The preload they set on the side bearings was high enough that the mineral oil did not lubricate effectively. Off roaders around here use mineral oil because it is cheaper. They change it more when it gets contaminated with water and mud, or break something.

thermorex · **Posted:** Wed Apr 20, 2016 3:41 pm

tcoilburner wrote:

The preload they set on the side bearings was high enough that the mineral oil did not lubricate effectively. Off roaders around here use mineral oil because it is cheaper. They change it more when it gets contaminated with water and mud, or break something.

I disagree that offroaders use mineral oil because it is cheaper. Maybe some country side hillbilly does that in his 1,000 bucks "offroad", but who is serious about offroading and spends tens of thousands on a capable vehicle setup won't go cheap out of the blue to save few bucks in cheaper oil Diff.

tcoilburner · **Posted:** Wed Apr 20, 2016 8:24 pm

I am will to guess, since no reason is given on truehi9.com, that no synthetic oil is to be used. That a synthetic oil will not stay on the ring gear long enough to travel to there channels to oil the bearings. The mineral oil sticks to the gears long enough to travel to the oil channels. Without out contacting them this is speculation.
Synthetic oils do better in most situations, but there are some situations where there properties work against them. As in high pinion axles. I hope I get this link right. http://www.machinerylubrication.com/Rea ... ional-oils

This one also. http://www.machinerylubrication.com/Rea ... c-gear-oil

kj75 · **Posted:** Wed Apr 20, 2016 10:58 pm

Some interesting articles.

According to this article http://www.machinerylubrication.com/Rea ... c-gear-oil

"Synthetic oils have better resistance to aging and high temperatures and a longer service life than mineral oils. Depending on the base oil (SHC or PAG), the oil change intervals may be three to five times longer at the same operating temperature."

Differental lube

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