[Guest]

Hey all,

Got a 91 YJ, 5 speed with the 4.0 engine and 4.11 differentials. Stock tires. I get about 15 mpg city driving, and I get about 15 mpg on the highway.

Also, at 65 mph in 5th gear, I am around 2900 rpms. It's tough for me to tell, since with the 4.11's, the speedometer and odometer don't work correctly.

Are the mpg numbers normal? (Yes I know, define normal) Does anyone have any numbers to compare?

Any suggestions on improving gas mileage?

Thanks,
Jess

 

[upalittle]

Its hard to know what your actual mpg is. Your odometer will be off the same percentage as your speedometer. So if your speedometer is off 15%, your fuel mileage will also be of 15%. I would guess your mileage is within limits, but possibly a little low. The larger tires, while causing more drag and air resistance, should still make a slight improvement.

 

[GeeAea]

go here!

Go and figure your true tire height ..and axle ratio and swap in the right gear.
When you've determined what tooth count you need ..go to your local Jeep dealer and ask for part # 520676XX ..the XX is the tooth count you need. So a #52067630 ..is a 30 tooth speedo gear.
...here's how in detail

After all that ...you'll only feel better or worse depending on what you will then be calculating your mpg by

 

[1070]

My $0.02..... my 89 was getting 10 or 11 when I bought it and now with a little TLC is acheiving the astounding mpg of 16-17. I'm not sure what condition yours is in but if its got 160,000 miles and terrible blow-by, you might not get much better.

 

[Guest]

Thanks for the feedback everyone. Especially the speedo gear calculator. I had a link to a different one, but the site was down.

I pretty much know how high everything reads, so I know how to adjust to get the correct numbers (About 4/3 too high, so reduce by 3/4). Obviously this will change with 33" tires. Hopefully gas mileage will improve a little.

Hey jeepsteve, it's only got about 110K miles. Not sure of the blow-by. What sort of TLC did you do?

Jess