I have recently bought a 2007 CRD Auto with 31,000 miles on the clock. Running around locally I am getting around 20 miles per gallon. We already have a 2004 CRD Auto with 95,000 on the clock which we have had from new. This does around 24 miles per gallon for local journeys. The 07 has recently had an oil and filter change, fuel filter, air filter and seems to run perfectly. It has just passed its MOT without any problems and produces no smoke on acceleration.
One thing I have noticed is that the torque converter on the older car locks at around 45mph whereas the newer one locks at about 53mph, so often the converter is not locked for local driving.
The question is why should it use so much more fuel, or is that just the way the later cars are? Is there something wrong with it? Any thoughts much appreciated.

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Wrangler TJ
Cherokee KJ CRD auto

Some thoughts:
1. it's certainly possible that the 07 has different gearing and/or rear end ratio than the 04
2. given the lockup I wonder if the 04 is a 4-speed automatic vs a 5-speed on the 07 which would explain the lower lockup mph. If so then depending on the actual driveline ratios the lower speed lockup could mean better local driving mpg.
3. don't know about the 04 or the 07 but on the 05 and 06 odometer reading vs actual miles traveled can be quite different. If the 2 vehicles odometers are off in different directions, so to speak, that could explain a lot of the difference. Acceptable error is +-5% IIRC so if one is +5% and the other is -5% there is a chunk of the difference. Get a GPS unit and check odometer vs actual miles.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Thanks papaindigo - I think the boxes are both 5 speed but I hadn't thought about speedo accuracy! I'll check it out. Don't know about final drive ratios but interesting to have a look and see if they are the same. Other than that both cars seem to drive very much the same.

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Wrangler TJ
Cherokee KJ CRD auto

You are probably right on the boxes; as nearly as I can tell the 445RFE transmission was not used on any KJ CRDs and it appears the 545RFE was used on KJ CRDs from 02-07. As to the rear end gearing I don't know but the DCJ vehicles I'm familiar with typically have a small metal tab on one of the rear differential cover bolts that's stamped with the rear end gear ratio.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Most of the 2007s are 3.73 final drive ratios.

FWIW, my speedo is a little overly-enthusiastic: when the the needle reads 70, the GPS says 66mph. The EVICS MPG is also consistently 3mpg over what the miles on the odometer divided by gallons purchased are.


-p

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2006 CRD w/99,300 miles
F31 from a previous life
EHM @ 42K, ProVent @ 79K
GDE Eco Tune & TCM @ 46K
Engine mounts replaced @ 55k/93k, Timing Belt @ 90k
Lift Pump @ 97k
OME Lift, 1.5''
Kenwood TM-V71 Ham Radio / Cobra C75WX CB
Surf Racks

Oh dear - does that mean it's even worse than I thought! I haven't yet checked either against the gps but will do so.

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Wrangler TJ
Cherokee KJ CRD auto

Speedo/odometer/EVIC never agree and at least as far as I know the speedo and odometer get their figures from 2 different sources so they can be off in different directions. Required accuracy is +-5%. The only way to tell is with a GPS. Speed can be check pretty much instantaneously but for odometer I favor 2-3 runs of at least 25 miles on a reasonably flat and straight road and average the results. Changing tires means you need to redo the figures; made a difference in my case even though the replacement tires were supposed to have the same diameter.

I understand that within limits a Dealer or someone with dealer equivalent scan tools can adjust the readings but how much I don't know.

EVIC sort of does it's own thing and should only be considered a guess although once you understand your EVIC mpg readings you can generally do a mental adjustment to get close to hand calculated GPS mpg figures.

PS I've seen several different CRDs and no 2 are alike in speedo/odometer/EVIC error.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

My original comments were based on the EVIC readings so probably not very accurate. A bit more work needed I think to see where it's really at!

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Wrangler TJ
Cherokee KJ CRD auto