Fuel Mileage

asonyi · **Posted:** Tue Jan 13, 2015 12:12 pm

Does anyone else notice a decrease in fuel mileage on the 2nd half of a full tank of fuel? My wife and I went away this weekend up to New Hampshire. Filled up the tank prior to leaving. Got about 320 miles on the first half tank which would estimate around 30 mpg with just about 100% highway driving, cruising at 70 mph. In the end, one way, from start to finish the trip was about 350 miles and used roughly 2/3 tank of fuel. On the way home, took same exact route except opposite direction and same speed and ended up going about 490 miles to a full tank before I had to stop on the highway to refill. The final math would result about 26 mpg on a full tank of gas. Just seems a little strange that mileage would decrease especially on 2nd half of trip considering driving conditions were pretty much identical. I'm not complaining much just pointing out something I noticed.

PALiftedKK · **Posted:** Tue Jan 13, 2015 12:34 pm

I get 100 miles from full to half then I usually get no more then 80 miles from half to about 2 gallons left.

be happy with those numbers. we gasser kj and kk owners would be happy to see 300. I've never seen anything above 250miles on 1 fill up. sorry im no help here. check air filter, maf sensor, and maybe reset ecu.

papaindigo · **Posted:** Tue Jan 13, 2015 1:23 pm

You cannot use fuel gauge needle position to estimate rate of fuel consumption; pretty much the same for all vehicles that I know of. On the KJ CRD the fuel gauge needle position is known not the be at all linear (for example 1/2 on the gauge does not equal you have used exactly or even nearly 1/2 the tank's fuel capacity). GDE's ECU tunes make the gauge more linear to a certain extent. Further complicating things is the listed "approximate" tank capacity of 20.5 (Owner's Manual) is probably +- 1 gallon or more depending on whether the pump cut off early or you went to the trouble of making sure to fully fill the tank to the point of having unfoamed diesel fuel at the top of the filler neck.

Bottom line - yes the fuel gauge moves at different speeds so to speak.

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

It's not that you're getting worse mileage the second half. If you have the factory ECU tune, the fuel gauge is non-linear.

asonyi · **Posted:** Tue Jan 13, 2015 1:54 pm

I have GDE ECO tune installed.

stp2136 · **Joined:** Sat Sep 29, 2007 8:30 am **Posts:** 35

Second that. In my experience with the GDE Eco tune the fuel gauge is correct at the 3/4, 1/2, and 1/4 points. That is, 15, 10, and 5 gallons left respectively. The gauge is highly nonlinear below 1/4 though--it drops like crazy--which is disconcerting when you are out in the boondocks 50 miles from the nearest station. Not to worry though as the tank holds at least 20 gal (possibly 22 if you are able to fill the expansion pockets?).

dirtmover · **Posted:** Tue Jan 13, 2015 2:03 pm

Unless things have changed in the couple of years since I purchased my GDE tune it only fixes the gauge on the '05, not the '06.

ebbnflow · **Posted:** Tue Jan 13, 2015 6:43 pm

The gauge in my 06 has never been linear. Had a GDE tune since 2010. First 1/2 lasts longer than 2nd half. Below 1/4 tank and it drops fasts. I seem to average 400-500 miles per tank if I dare go into below 1/4 tank land.

Fuel Mileage

Who is online