MPG... I know, I know

Prime8

Prime8

New member
Just wanted to get some input, since I think my mpg is far below where it should be for a 2013 JKUR automatic with a 3.6 Pentastar. I average about 11.5 mpg, mixed highway and city driving, according to the dash readout. The potential mods affecting this are:
37" Nitto Trail Grapplers
17" Spyderlock beadlocks
EVO 1/4 Pounder w/ stinger
EVO rock skins and rear tire carrier
LoD sliders
4.10 gears
ProCal
EVO Double D long arm kit
JE Reel 1350 front drive shaft

Those are the only mods I can think of that add significant extra weight or would change driving dynamics. I know that's a lot of weight, but I was running 35" GY kevlars on my 2010 with similar mods (minus the bumpers) and getting 13.5 average mpg!

Any ideas...?
 
P

Pushrod

New member
Have you changed the parameters in your Jeep computer telling it you were running larger tires with a programmer? Until you do that it is not going to give you an accurate calculation on the MPG and you may be getting better than you think. The larger tires make the computer calculation wrong until you program in the correct size. I see you have a calibrator but you didn't specify the change has been made.
 
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DBTJKU

DBTJKU

New member
Pushrod said:
Have you changed the parameters in your Jeep computer telling it you were running larger tires with a programmer? Until you do that it is not going to give you an accurate calculation on the MPG and you may be getting better than you think. The larger tires make the computer calculation wrong until you program in the correct size.
Click to expand...

They have a Procal.
 
Prime8

Prime8

New member
Pushrod said:
Have you changed the parameters in your Jeep computer telling it you were running larger tires with a programmer? Until you do that it is not going to give you an accurate calculation on the MPG and you may be getting better than you think. The larger tires make the computer calculation wrong until you program in the correct size. I see you have a calibrator but you didn't specify the change has been made.
Click to expand...

You mean you can't just stick the procal in the glovebox and have it automatically and wirelessly converse with your ECU? Haha, of course it's calibrated... To both 4.10 gears and 35" ground-to-shoulder tire measurement....
 
Prime8

Prime8

New member
Gas lip? I'll start manually tracking it, but if it is calculating my mpg incorrectly, how can I trust the odometer readout to be accurate for manual calculation...?
 
Notajerryskid

Notajerryskid

-
I did mine the old fashion way 3 times against the computer. My computer was with in 1/2 mpg average.

37 Nittos
EVO front bumper/ stinger
EVO rear tire carrier
EVO side rails / armor
4.10 gears
6 speed
Banks cold air intake
Soft top

I average 16-18mpg.

I'll ask a friend what he is getting right now. His is a 12 with 37's and 6 speed with cold air also.
 
Prime8

Prime8

New member
Thanks brother, I can't imagine the CAI is giving you 5+ mpg, but if it is I know what my next mod is!
 
Tackerdown

Tackerdown

Banned
Lol( slip) that's a good question but by doing so it will still give you a point of reference . It may or may not point out a specific problem but if you do get two different reading you at least have a starting point . Iv noticed on our 2011 (stock) I need to reset it some times .

C.O.D.
 
MTG

MTG

Caught the Bug
If its more city than hwy, or you drive fast (over 65) on the hwy like me, I'd say it's pretty close. What were you getting before lift and tires?
 
MTG

MTG

Caught the Bug
I think with 4.10s I was getting between 11.5 and 13.5 depending on my driving habits. I'll check today but I think I'm around 12.5 with 5.13s. That is mostly hwy and I've been trying to keep it under 70.

My computer with procal was always within a few tenths with a hand calc.
 
OverlanderJK

OverlanderJK

Resident Smartass
If you have your tire size at 35" I would bet that is your issue. I find it hard to believe that the tire size is 2" difference from what it should be. Do the chalk test to make sure your accurate.

I would also do it by hand and see where you are at. I am getting 19-20 mixed and can get 23 if I go 65 mostly highway.
 
GCM 2

GCM 2

New member
Don't forget to also factor in that your rig is lifted. You have effectively increased the frontal area of your jeep by exposing more things on the underside to become a wind break. All the extra mods do add weight, which is part of the decrease in mileage, but disrupting the airflow has a huge effect. Some people find this hard to believe, but it's no different than taking a really slippery body design and then throwing a roof rack/luggage hauler/bicycles whatever you want on top. It turns smooth a smooth surface into a sail. The same holds true for the underside of a vehicle, when you lift it, now everything starts to grab air. Sucks, but thems is the facts jack, add heavy parts and raise a vehicle and your mileage drops.
 
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