Unhappy with MPG - looking for ideas

[Chief20]

I checked the EVIC: the Tazer modes I had entered are still there.

The speedometer came a little off from the factory; it overstated my speed by 1 MPH, so when I re-calibrated the speedo for 35-inch tires, I played with the tire size to get the speedo to be spot-on.

I now went ahead and changed the tire size settings from 33.75 to 34.0 inches --my 35s measure 34 inches mounted. I will see if that helps with the shifting.

Hey i got 3.45 with 35’s (66lbs) and stock rim (23~lbs) and 3inch lift. With tazer i get mixed about 18-19. Stopping and going will kill mpgs on the 3.45’s. Maybe do a engine fuel cleaner system and try a different gas grade. My tire measures to 34.8 and i put 35 on tazer.

Sponsored

 

[aldo98229]

Hey i got 3.45 with 35’s (66lbs) and stock rim (23~lbs) and 3inch lift. With tazer i get mixed about 18-19. Stopping and going will kill mpgs on the 3.45’s. Maybe do a engine fuel cleaner system and try a different gas grade. My tire measures to 34.8 and i put 35 on tazer.

Thanks. Yes I just poured a bottle of Techron fuel system cleaner. Let's see what it does.

 

[Chief20]

Thanks. Yes I just poured a bottle of Techron fuel system cleaner. Let's see what it does.

Just do the measurements of it correctly.

 

[aldo98229]

Just do the measurements of it correctly.

Haha! Yeah. I read the instructions this time...for a change!

It says to use one bottle in up to 12 gallons of gasoline; more Techron if more cleaning is needed. I poured one bottle in approximately 10 gallons of gas. I plan to top it off with gasoline from a Chevron station.

 

[Chief20]

Haha! Yeah. I read the instructions this time...for a change!

It says to use one bottle in up to 12 gallons of gasoline; more Techron if more cleaning is needed. I poured one bottle in approximately 10 gallons of gas. I plan to top it off with gasoline from a Chevron station.

I read that after that tank, fill up of just fuel and flush that out of remaining cleaning fluid. It cant hurt

 

[aldo98229]

I took the Jeep out for a short drive. It appears that setting the tire size from 33.75 to 34.0 inches "freed" the transmission to shift up more readily.

I haven't driven it on the highway yet, but around town, at 35 MPH it was already shifting into 6th gear. So that is an excellent sign!

Using all 8 gears alone will go a long way towards improving fuel economy.

PS - I also turned on ESS and it is kicking in, so the batteries are fully charged.

 

[Chief20]

I took the Jeep out for a short drive. It appears that setting the tire size from 33.75 to 34.0 inches "freed" the transmission to shift up more readily.

I haven't driven it on the highway yet, but around town, at 35 MPH it was already shifting into 6th gear. So that is an excellent sign!

Using all 8 gears alone will go a long way towards improving fuel economy.

PS - I also turned on ESS and it is kicking in, so the batteries are fully charged.

For the tazer, did you do the 2 sleep cycles and a long drive as stated?

 

[aldo98229]

For the tazer, did you do the 2 sleep cycles and a long drive as stated?

I did the 2 reboot cycles. Haven’t done a long drive yet.

Will do the long drive tomorrow when I take the Jeep 30 miles to the dealer for the TSB.

 

[Yogi]

All things being equal vis-a-vis rolling mass, and no other electronic changes, a sudden drop off in fuel consumption would indicate a tuning issue. I'd be looking at the easy things first like air filter, oil levels, and so on. If all looks good there, then on to tier 2 diagnostics. Things like spark plugs, coil packs, etc. If not those, then you're into things like the ECM.
Anyways, I'm out of time to delve into this further, but that's where I'd be looking first.

 

[entropy]

Are you driving around town a lot? once you add heavy tires and the stock gearing your engine has to work a lot to get them rotating. I average about 15mpg city and I am only on 33 falken M/Ts. I can get 17~18 if I feather the pedal. There's like a million stop lights where I live, and hills since I live on the foot of the san gabriels.

On the freeway it is a different story. I can get up to 25mpg on a good day and feathering the pedal a lot. 21~22mpg If I drive normal.

 

[mwilk012]

My automatic transmission won't shift into 8th gear on the highway; it will barely shift into 6th at 75 MPH, and into 7th going downhill and with a tailwind. So shifting is clearly part of the issue.

What I don't know is if the transmission is holding onto lower gears because of the tires or something else --e.g., loss of power, the alternator running constantly, carbon buildup, etc.

You need to regear.

 

[WOwen]

Well whatever you do DO NOT get a 392 and put 37's on it! You'll really hate your gas mileage! I spend more in gas on my Jeep then I did my M6 Hellcat. Well worth it

 

[ekim]

If the brakes are dragging enough to kill the milage like that then you will be able to tell by touching the wheel - **not the brake itself or the rotor!!**. The dragging brake will be hot or way warmer than the others.

 

[aldo98229]

Re-setting tire size to 34.0 inches (up from 33.75) has helped the transmission shifting around town, but it barely budged on the freeway.

I now routinely get the transmission to shift into 6th gear around town. That is progress from where it was before.

Just did a 25 mile drive, sustaining 70-80 MPH: it averaged 15.2 MPG on mostly freeway driving. Not great, but slightly better than it was. The transmission now shifts into 7th, and will only shift into 8th if I'm going downhill.

All in all, looks like I gained 1 or 1.5 MPG, most of it in city driving, by simply re-setting the tire size.

The Jeep is now at the dealer getting the steering box TSB done, so I can't try anything else until I get it back.

 

[aldo98229]

If the brakes are dragging enough to kill the milage like that then you will be able to tell by touching the wheel - **not the brake itself or the rotor!!**. The dragging brake will be hot or way warmer than the others.

Yeah, the brakes appear to be working normal.

Sponsored