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Diesel Fuel Mileage Does Vary

558 views 4 replies 4 participants last post by  EFSiR 
#1 · (Edited)
I just returned from a 2,300 mile trip. I filled up four times. As to my subject title, my first and last fill ups were steady driving. My instrument panel mpg gauge showed 42.4. When I filled up, my cdi took 19 gallons, while I traveled 652 miles. That comes out to 34.3 mpg, not what the instrument gauge showed. My last tank was about the same, I went 631 miles on 18.8 gallons of diesel, which averaged out to 34.4 mpg, not 41.4 the instrument gauge showed.
I always thought the instrument mpg gauge was more accurate than that?
I cannot complain because the car performed flawlessly. I have 143k miles on my cdi. For my next tire change, I may replace some front suspension parts. I do hear a slight creak (crunch) the first time I back out of the driveway with the wheels turned slightly. I had the lower ball joints replaced at 50k. My cdi seems to drift some while going down the highway, but it always did that. My other concern is the water pump and of course the sbc.
Thanks for listening!
Mike T.
 
#2 ·
The computer calculations are notoriously skewed high. In my case, they are about 3.1 mpg higher than what I actually measure tracking every mile and every gallon. Looks like yours is skewed even higher...I talked to another forum member whose CDI consistently read 6 mpg above what he was actually getting.

Great car...but don't trust the fuel economy figures.
 
#3 ·
My cdi with 271000 says about 40-42 on the dashboard. It's gotten higher the last couple of years. When I check using a calculator on trips, I will get 38-39, still pretty good. I've been keeping track since I bought it new. It says it gets 21-23 around town. I don't believe it. It does run good and not many problems so it's a good car. steve
 
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