22 mpg ?

adrianmiura · **Posted:** Sat Jan 21, 2012 11:12 am

Any ideas why my fuel economy has not increased with the Eco Tune?
If I drive (Highway) at 2000 rpm's I get 27 mpg if I drive (Highway) at 2500 rpm's i get 22 mpg.

here is some background.
1. the vehicle is driven at an average altitude of 5200 feet
2. run PS Diesel Kleen
3. Tires 245/75 16 Michelin AT2 (40 psi)
4. New Air Filter Wix
5. New Thermostat,water pump, timing belt
6. New oil filter amsoil

Thanks for your time
Adrian Miura

nursecosmo · **Posted:** Sat Jan 21, 2012 12:06 pm

That sounds about right. I have the same tires and my mileage goes up significantly when I switch out to my snow tires in December. The air resistance against our mobile bricks increases very quickly and almost exponentially the faster we are moving. See this article: http://phors.locost7.info/phors06.htm These AT2 tires also appear to have much larger than usual rolling resistance. Just be glad that you're not driving a Gasser, you'd be getting <15 MPH.

DOC4444 · **Posted:** Sat Jan 21, 2012 12:14 pm

EHM, eliminate brake drag, unplug CAT.

DOC

naturist · **Posted:** Sat Jan 21, 2012 10:17 pm

Winter diesel will chop 10% right off the top, so depending on when you installed it, that could make all the difference in the world. 27 on the highway is perhaps a tad low, but then again, if you are USING the extra horsepower the ECOtune delivers, don't expect a mileage jump. Mileage only goes up IF you keep your foot off of the loud pedal.

I installed the ECOtune back in August, and saw about 15% bump. Best I'd ever gotten before was a hair over 30, best since has been 34.7, but my average during the summer was around 25, now it's around 27, with the mix of short and long trips in town/on highway that I normally pull. Best I've gotten on winter diesel is just over 29.

It should always be noted that how one drives is known to make 30% difference from worst driving habits to best. There is leeway in there, obviously, to cover all kinds of things, and easy to lose track of some vehicle change that might otherwise make 15% difference.

adrianmiura · **Posted:** Sun Jan 22, 2012 11:34 am

Thanks for the replies,
I have never seen 30 even with the "stock" tires. I have been running the ECO tune for ~2 years now and the MPG measurements were done on strictly highway trips between Albuquerque and Santa Fe so it was very easy to set cruse and keep it at a consistent rpm.

eliminate brake drag, sorry to be so dense but not tracking here. break pad dragging on the rotor?

Im wondering if altitude could be a factor?

nursecosmo, good to see a fellow ham I'm W5ASM,

papaindigo · **Posted:** Sun Jan 22, 2012 12:52 pm

Altitude could matter. On brake drag - drive a short distance, couple of miles, without using brakes or using them as little as possible then stop and see if you have hot wheel(s); get each wheel off the ground and see how they spin by hand. Front brakes have a rubber boot that tends to bind and prevent pads from retracting and the rears have a funky parking drum brake inside the disc that can drag.

CATCRD · **Posted:** Sun Jan 22, 2012 3:46 pm

I get my best fuel mileage at high altitude. The higher the better because of lower wind resistance, so I don't see that being the cause. Maybe you have an intercooler leak? It's not hard to make a test kit using some PVC pipe caps and an old valve stem.

CIMARRON13 · **Posted:** Sun Jan 22, 2012 9:10 pm

I would be happy if I got 22. I get a solid 19, 20 with 245/75 MTRs, Eco tune, 4.10s, and heavy armor. I drive pretty slow as well. Sometimes on road trips I can squeeze out 23.

DOC4444 · **Posted:** Sun Jan 22, 2012 9:25 pm

The front calipers have one slider pin each that has a rubber sleeve (presumably to kill rattles). However, these "grow" a tiny bit and jam the caliper. Best fix is to permanrntly remove the sleeve. If you heavily lube with special slider lube, they won't rattle. With the rig on stands, you should be able to wiggle the calipers on the pins. If they won't budge, you need to take them apart, throw the sleeves away, lube and reassemble. I have not done my rears yet so I don't know what the story is with them.

Also KJ front caliper hoses collapse internally at some point, keeping the piston from retracting when hot. This goes away after cooling, so it can be hard to find. Also, the phenolic pistons eventually start seizing. When you try to retract the pistons to install new pads, if it is really hard, replace the calipers.

We average 32-34 mpg in summer in mixed driving/27-29 in winter. This requires 195 degree coolant temp, blocked cold air intake (winter), fan removal in winter and no parasitic drag to acheive. Check my sig for details. GDE claims "clean" CAT does not help, but I'm not sure.

DOC

adrianmiura · **Posted:** Tue Jan 24, 2012 1:28 am

ok looks like i have some work to do this weekend
1. check the inter cooler for leaks
2. parasitic break drag

Thanks

dirtmover · **Posted:** Tue Jan 24, 2012 9:46 am

I wouldn't worry. Your figures sound fairly typical. I've been getting a consistent 20 in the Winter, 25 in the Summer and somewhere in between for Spring and Fall for the 6 years I've owned this vehicle.

Don't get mislead by the guys that brag about getting 30mpg. This is the exception rather than the norm. You can only get it this high by babying it and with almost exclusively highway driving. I did, however, hear a rumour that Betty White just got herself a CRD for her 90th birthday and is getting pretty good mileage :-)r

tjkj2002 · **Posted:** Tue Jan 24, 2012 12:21 pm

nursecosmo wrote:

Just be glad that you're not driving a Gasser, you'd be getting <15 MPH.

Hey I get 17mpg's on the highway,not bad for 3 tons of fun rolling on 35" MT/R Kevlars.

warp2diesel · **Posted:** Tue Jan 24, 2012 5:32 pm

Check your odometer error.
With my 215-85-R16 Coopers I have to multiply the odometer reading by 1.115 (115%) to correct the error. I know it is only an 11.5% increase in the miles, but when you get reimbursed fore mileage like I do, you have to be dead on with the figures you use or else.

DOC4444 · **Posted:** Mon Jan 30, 2012 5:37 pm

Is your viscous heater diabled? If not running at 195 degrees coolant temp, the VH never shuts off. Check my sig. VH kills mileage by 3-4 mpg when running. We recently have been waiting for our dealer to get in a backordered part and have the Jeep configured for a dealer visit. As such, we have been running the stock ECU and getting 22 MPG (usually 28-30 in winter).

DOC

22 mpg ?

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