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Poor gas mileage

I have a 98 jeep wrangler with the 4.0L straight six engine. I get 15-16 mpg driving ~50 mph or ~70 mph. The tailpipe is always black and sooty.

The mileage is ~8000 (just getting broke in?).

The dealership says this is normal! I have a 98 Ford club wagon with a 4.6 v8 that gets better mpg.

Looks Like EPA Says 16 Hwy For The Automatic And 19 Hwy For The 5 Speed Manual.


8,000 miles on an 11 year old Jeep?
I sure hope that you have been maintaining it on the basis of elapsed time, rather than on the basis of odometer mileage!

Although the gas mileage that you report is really not bad for that model, it is possible that poor maintenance has something to do with the mileage that you are getting from it. Can you give us some specifics on how often this car has been serviced?

Normal. The problem is the complete and utter lack of any aerodynamics and gearing. Remember your Wrangler is built to go off road at (very) low speeds not highway travel.

Jeep Wranglers aren’t built for mpg. They are boxy, have very poor aerodynamics, are geared for off road use, and have off road tires. If it is an automatic trans you are getting the correct mpg. You’ll get much better mpg at 50 mph than at 70 mph as the drag from the wind is much higher at 70.

To get the best mpg it can give you, keep it tuned up (new plugs, wires, dist cap), replace the air filter, make sure there is no drag from the brakes and wheel bearings, and keep your speeds on the interstate at 55.

If you want to make modifications to improve mpg, change the tires to more of a “street” summer type tire, and change your differential gear ratio’s to lower your rpm at highway speeds. Neither of these mods is good for the Jeeps prime mission of going off road but will yield more mpg.

Your Jeep is rated for 13 MPG city, 16 on the highway if it’s an automatic. If that’s what you’re getting then your Jeep’s mileage is dead on normal.

The sooty tailpipe might be oil burning, if it hasn’t been getting an oil change at least once a year, preferably twice, regardless of mileage.