CRD Engine Break-In Period ??

Cowpie1 · **Posted:** Sun Aug 13, 2006 10:20 am

Very good analysis, OldNavy. Couldn't have said it any better!

I often wonder if the rear air deflector I have on my CRD helps with the aerodynamics. I live on a gravel road so I had it put on mainly to keep road dirt off of the back window, which it does. With the air flow helping to overcome the blocky rear end, it would seem to be advisable for all Liberty owners to have the rear air deflector on their ride.

dgeist · **Posted:** Sun Aug 13, 2006 10:42 am

Katmandu wrote:

How many miles need to be put on a CRD until they are considered "Broken-In" ??

Basically, at what point are you'all seeing DECREASED Fuel Consumption due to a "Broken-In" engine ?? :?:

I have about 4800 on mine currently. It's been a gradual increase for me, but the slope of increased fuel economy got much steeper around 3k. I just made a trip out of state and averaged 26.1 on highway with the AC on and lights about half of the way due to rain. It would have been better, but I kept the speedo at 75 (slightly higher than optimum, IIRC).

Dan

oldnavy · **Posted:** Sun Aug 13, 2006 11:52 am

One thing I failed to mention is the fuel differences, most here probably even when buying "Premium Diesel" are only getting 42 cetane fuel. I would go through the routine explaining what is/can be labeled as "Preminum Diesel" and what minium the cetane can be in premium or standard diesel fuel, but you all need to research that yourselves. Just remember if you are getting clean 42 cetane fuel you are lucky, a very small % of us are getting 48 to 50 cetane, with a small percent getting that cetane plus 2% to 99% biodiesel. This high quality fuel will help increase MPG's, quiten the engine and decrease smoke, and this is also what ULSD should do for all of us here. Just think maybe 50 cetane B10 or B20 diesel becoming common in the near future.

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

Highest, 32, City Lowest: 21. Usually 26 combined. I drive mainly highway-- but sometimes it is slow stop and go during rush hour. 4-wheeling-> I get 21-23.

At 75-80 mph, mileage averages 25 mpg highway.

I have noticed that with some fillups I get better mileage than others and that I can not find a consistently high quality fuel source-- every station seems to have variances. One tank will have good mileage and pep and the next feels sluggish and mileage is poor. I have remedied this by adding PowerService. It seems to get me slightly better .8mpg, and much more consistent mileage and pep. I suppose that it helps bring the bad fuel up to par with the good.

I noticed that adding the new muffler got me an increase of 1.5 mpg. It was more at first, but my data went down as the muffler stayed on longer.

The biggest increase, however, came from putting more air in the tires-- about 3.5 mpg at 42psi over 32psi. I am currently running 38psi front and rear on stock tires, as it is summer in AZ, and I would rather error a little on the low side. If your tires are at the traditional 32psi-- that may be your problem. Also note that higher quality (higher traction) tires may actually get worse gas mileage. When I put top-of-the-line touring radials on my other car, traction went up and handling increased-- but I lost 4mpg. (Traction usually equals more rolling resistance). I would suspect that tire type,tire pressure, clean air filters, and fuel quality have the most to do with the variances in mileage between CRD's.

oldnavy · **Posted:** Mon Aug 14, 2006 8:05 am

Pablo wrote:

Highest, 32, City Lowest: 21. Usually 26 combined. I drive mainly highway-- but sometimes it is slow stop and go during rush hour. 4-wheeling-> I get 21-23.

At 75-80 mph, mileage averages 25 mpg highway.

I have noticed that with some fillups I get better mileage than others and that I can not find a consistently high quality fuel source-- every station seems to have variances. One tank will have good mileage and pep and the next feels sluggish and mileage is poor. I have remedied this by adding PowerService. It seems to get me slightly better .8mpg, and much more consistent mileage and pep. I suppose that it helps bring the bad fuel up to par with the good.

I noticed that adding the new muffler got me an increase of 1.5 mpg. It was more at first, but my data went down as the muffler stayed on longer.

The biggest increase, however, came from putting more air in the tires-- about 3.5 mpg at 42psi over 32psi. I am currently running 38psi front and rear on stock tires, as it is summer in AZ, and I would rather error a little on the low side. If your tires are at the traditional 32psi-- that may be your problem. Also note that higher quality (higher traction) tires may actually get worse gas mileage. When I put top-of-the-line touring radials on my other car, traction went up and handling increased-- but I L.O.S.T. 4mpg. (Traction usually equals more rolling resistance). I would suspect that tire type,tire pressure, clean air filters, and fuel quality have the most to do with the variances in mileage between CRD's.

Very well said Pablo, I do the same with my tires. I run 40 psi all around now and it does make a big difference as you say.

PSI: I have been doing this for years, using the 10% back rule on the Max rated PSI on the tire. I have many miles on tires running across the desert SW at high speeds with 40 to 45 psi in tires depending on tire type & mfg rating.

Bovie · **Posted:** Mon Aug 14, 2006 1:21 pm

Pablo wrote:

I have remedied this by adding PowerService.

I had made a post a few weeks back about adding Stanadyne's Fuel additive to my tank. Is there anyone else using additives?
I think it might be worth trying.

oldnavy · **Posted:** Mon Aug 14, 2006 1:29 pm

Bovie wrote:

Pablo wrote:

I have remedied this by adding PowerService.

I had made a post a few weeks back about adding Stanadyne's Fuel additive to my tank. Is there anyone else using additives?
I think it might be worth trying.

I never go anywhere without my PowerService, that's for sure.

KJbob · **Posted:** Mon Aug 14, 2006 1:50 pm

I just switched over to Power Service because it's more readily available (at my local Walmart).

I've always used additives in my diesels and was surprised when my Jeep dealer told me not to use any in my CRD.

Bovie · **Posted:** Mon Aug 14, 2006 2:52 pm

Oldnavy, I wonder if that is part of the reason you get great milage with the CRD.
1) You drive in it's Power Band (1800-2000rpm's)
2) You have good fuel
3) You use Power Service?

I think I might try Stanadynes preformace fuel additive at lease until I can buy ULSD. Wonder if it would help the mileage.

Bovie · **Posted:** Mon Aug 14, 2006 2:53 pm

Also I didn't see anything in the manual saying not to use additives.

oldnavy · **Posted:** Mon Aug 14, 2006 6:06 pm

Bovie wrote:

Oldnavy, I wonder if that is part of the reason you get great milage with the CRD.
1) You drive in it's Power Band (1800-2000rpm's)
2) You have good fuel
3) You use Power Service?

I think I might try Stanadynes preformace fuel additive at lease until I can buy ULSD. Wonder if it would help the mileage.

1.) Yes, I do try most of the time.
2.) Yes, that for sure helps.
3.) Yes, I do.
A.) I keep tires inflation up properly with OEM Goodyears at 40 PSI.
B.) I use all synthetic oils.
C.) I use a low restriction muffler

Endurance · **Posted:** Mon Aug 14, 2006 6:55 pm

oldnavy wrote:

Bovie wrote:

Oldnavy, I wonder if that is part of the reason you get great milage with the CRD.
1) You drive in it's Power Band (1800-2000rpm's)
2) You have good fuel
3) You use Power Service?

I think I might try Stanadynes preformace fuel additive at lease until I can buy ULSD. Wonder if it would help the mileage.

1.) Yes, I do try most of the time.
2.) Yes, that for sure helps.
3.) Yes, I do.
A.) I keep tires inflation up properly with OEM Goodyears at 40 PSI.
B.) I use all synthetic oils.
C.) I use a low restriction muffler

I dont know about my fuel quality, but besides that Im doing the same things and I get 20.5 mpg with 60% highway driving.

oldnavy · **Posted:** Mon Aug 14, 2006 7:36 pm

Endurance wrote:

oldnavy wrote:

Bovie wrote:

Oldnavy, I wonder if that is part of the reason you get great milage with the CRD.
1) You drive in it's Power Band (1800-2000rpm's)
2) You have good fuel
3) You use Power Service?

I think I might try Stanadynes preformace fuel additive at lease until I can buy ULSD. Wonder if it would help the mileage.

1.) Yes, I do try most of the time.
2.) Yes, that for sure helps.
3.) Yes, I do.
A.) I keep tires inflation up properly with OEM Goodyears at 40 PSI.
B.) I use all synthetic oils.
C.) I use a low restriction muffler

I dont know about my fuel quality, but besides that Im doing the same things and I get 20.5 mpg with 60% highway driving.

Fuel quality can and does make huge (anywhere from 5% to maybe as much as 20%) difference and that could be the problem. I remember with my '83 MB 240D the difference between 50 cetane & 40 cetane fuel was the difference in 32 MPG and a smooth, very quite engine, where 40 cetane would get me 25 mpg and a very noisy engine. Our VW's were not effected as bad as far as mpg 's went, only about 3 mpg for those cars for some reason. My guess the electronic's was the reason.

Bovie · **Posted:** Tue Aug 15, 2006 12:33 pm

Is that 40psi cold for the OEM Goodyears. From the stealership mine were at 31psi cold in the morning to 35/36psi after getting to work. I have the PSI monitor.

oldnavy · **Posted:** Tue Aug 15, 2006 1:01 pm

Bovie wrote:

Is that 40psi cold for the OEM Goodyears. From the stealership mine were at 31psi cold in the morning to 35/36psi after getting to work. I have the PSI monitor.

Yes that is always how you measure the air pressure, cold. With running the tires heat up and the air expands, that is why the tire mfg says on the side of the tire to check pressure's cold.

Bovie · **Posted:** Tue Aug 15, 2006 1:15 pm

40PSI just seems a little high.

oldnavy · **Posted:** Tue Aug 15, 2006 1:34 pm

Bovie wrote:

40PSI just seems a little high.

Been doing it for over 22 years since was told how to care for my tires by a tire engineer from Goodyear racing. Take the max cold pressure and set your pressure 10% back of that or 15% if ride is more important then wear of the tire. Anything more then about 25% back of that rating is getting in the danger zone for for tire to over heat at highway speeds and blow out. Our Jeep list 32 PSI as minium PSI, if I remember correctly, for the tires and that is about 25% back of the 44 PSI listed for max PSI with max loading weight on the tire. Why everyone is stuck on the 28 to 32 PSI is back in the 50's through the 70's the max ratings on most tires was 35/36 psi and everyone ran them at 28 to 32 psi, then came radial tires and people thought they were not inflated enough even though they had the same max psi rating and they had big problems with people have blow outs and bad tire wear.

I have never had a tire failure and get good mileage out of my tires, except when running cheap tires like the OEM Goodyears that come with the Jeep. :roll:

Jeger · **Posted:** Tue Aug 15, 2006 2:15 pm

I have always ran my tires on the high side as well 40PSI or so. Except when I had a suzuki samurai, it got to be a little to punishing with high pressures on it. But otherwise everything else has been fine.

no-blue-screen · **Posted:** Tue Aug 15, 2006 3:08 pm

I normally run all my cars at 85% of the max sidewall pressure. For the stock tires, mine show 44psi so I run them at 38. This gives me the best all-around performance and fuel economy. Do note that increased tire pressures will reduce traction in wet or slippery conditions and may not be ideal for all driving situations. If there is any question in your mind, just run them at the recommended PSI.

Bovie · **Posted:** Tue Aug 15, 2006 6:41 pm

I guess I might put a couple more pounds in them.

CRD Engine Break-In Period ??

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