dirtbiker117

I've owned my '89 XJ for about 13 months now, and the entire time I've struggled with the fuel economy. When on the highway, I have nothing to complain about. 20-23 MPG is normal. But whenever I'm in town...it's another story entirely, and it gets anywhere from 10-12 MPG.
I am a student, so virtually all of my trips in town are ~5 miles or less, which means that I'm running at less than full operating temperature for most of the trip.

I would expect some drop from the temperature being sub-operation a lot of the time...but is that much really to be expected?

On a different (possibly related?) note, sometimes the engine seems to have quite a bit of power...and at others, quite gutless. Generally the first 30 seconds to a minute of running seem to have decent power, and then it drops off.

Anyone have any idea as to either of those?

freegdr

that sounds about right i get clopse to the same mpg

draperndt

About the power dropping off after a minute of running: I could be wrong, but I think the O2 sensors don't come on until they reach a certain temp. That is when the electronics really take over on the motor. Because of the year of your XJ, it is easy to scan the computer. Turn the ignition on, off, on, off, then leave it on. The check engine light will flash. It is giving you 2 digit codes. Count the flashes until there is a break, 1st digit, count the flashes after the break, second digit. Then it's on to the next code. I don't have a list of the codes with me. But if you can't find them I could look it up. I have them somewhere.

dirtbiker117

Yeah, you're right about the sensors not kicking in for a minute or two...closed loop vs. open loop and all that.
But sorry, '89 is a RENIX, no check engine light.

So a complete halving of gas mileage is to be expected in town vs. highway?

By the way, the O2, TPS, MAP, and MAT are all new, CTS checks out fine.

giwill

If you want gas millage your probably going to have to get a Honda lol jeeps are just for fun not to be good on gas mine gets horrible gas millage specially with 33" and me as the driver and lead weights on my feet

jeep93

giwill's right.. jeeps have many strong points, but fuel economy isnt one of them!. I have a 1993xj 4.0 and it gets 18ish on the motorway, and 8-12 around town.. I live in the uk, so the fuel costs were killing me. I bought a 2nd jeep for daily running- a 1998xj 2.5L turbo diesel with a 5 speed manual transmission.. it gets around 26mpgs average, still poor for a diesel. I keep my 4.0 for the weekends!.

notop46

Hi dirtbiker,

We are in similar vehicles with the same size tires. I get around 18-19 highway at 80 MPH and 15-16 in town with a 5 speed. Depending on lift, other aerodynamic features (bumpers, roof rack...), and gearing your highway mileage is better. The same tall gears that help on the highway will hurt around town if you are trying to keep pace with sedans light to light. I keep my weight down with minimal stuff in the rear and hypermill when I can (Google hypermilling) even to the point of shuting off the engine if I know I will be at a light for a long time.

When my O2 sensor went bad, my mileage dropped 2.5 MPG across the board. with your highway mileage being good, I doubt that this is a problem. Check rear end ratio and see if this is a posibility.

I hope some of this helps.

dirtbiker117

Thanks for the replies everyone, guess I'm just stuck with not too great of gas mileage haha.

gmv93

jeeps are nice cars. i think same for most of older american cars too. since i have opportunity to know european cars better than american made becaause of living in a different country, i know all are same when you are doing short trips in the end. because of your o2 sensors work when they reach a treshold temperature due to their design, you will consume lots of fuel.

if you travel relatively short distances and if you do not have so much hills like i have here, why not to buy a good bicycle from a well know manufacturer? Trek works. they have nice carbon fiber mountain bikes. and you can carry it with your truck as well. or invest on an electric bike and a solar panel?