My first tank got me 14.3mpg with mostly city driving.
My second tank was 19.7mpg, and was highway for all but about 60 miles.
My current tank is on pace for about 12mpg (100% city).
If I go any lighter on the throttle, I'll get run over.

I have a 1987 3/4-ton 4x4 Chevy with a warmed up carb'd 350, and it gets almost 10mpg city with no carb tuning other than setting the idle. I also can't keep myself from getting on it every once in a while. Why does an EFI 4.0L in a vehicle that weighs 40% less only get two more mpg? Is it all the emissions garbage?

 

Im getting 8 mpg

 

the only answer is its a jeep lol i think i get 10 with mine

 

I'm getting 17.5 in mine. 50/50 highway /city. It's also all stock ( not lifted or any external extras).

 

Yeah, mine is bone stock too, except one of the previous owners had a hitch installed.

 

14.3 city and 19.7 highway is absolutely right in there for what to expect with a 2000 XJ with a 4.0

The EPA estimate is 16-21, and I have found that to be quite accurate to real life numbers.

Not much for a tuneup on a 2000 except keep fresh plugs in there and air filter. Don't use Bosch; the best plug for the 00-01 is the NGK and of course, gap checked to ensure .035.

 

Something that me personally have noticed is that.Wal-mart gas sucks. For me at least it burns up really really fast.

two different tanks from wal-mart , one ..i did 10mpg , and the second..i did 13mpg

But i do not see these same numbers when i go to like Quicktrip,or BP

 

Wifes 89 Aw4 Renix bone stock 20mpg city/hiway. My 94 5spd, 30/9.50 tires, 2" lift, roof rack, 17mpg city/hiway. Mine likes ARCO gas way better than Shell.

 

Bad gas mileage is a sure sign that the 02 sensor before the Cat is going/gone bad...Tj

 

I tuned mine up, cold air intake, new O2 sensors, cleaned the throttle body, royal purple synthetic oil, and run 93 octane gas and the best I have been able to get is 19mpg all highway, averages more like 17mpg. It's a jeep thing I guess. I have a friend with a liberty 3.7L and gets the same mileage as my 4.0.

 

The first tank was Admiral, the second was Sunoco, and third (current) is Marathon. Maybe my Jeep just doesn't like Marathon gas? That explanation is preferable to having to do a tune-up and/or replace the upstream O2 sensor. I'll keep an eye on the mileage and see what happens.
Thanks for the help.

 

It's been stated that gas with the ethanol blend will give you lower MPG's. I use nothing but Shell, as I don't know of a better brand of gas to purchase around here. My last tank of 93 octane got me about 21 MPG on a trip down to southern Illinois for new years.

 

I agree that Shell is probably the best gas available around here, but I don't know if it's 100% gasoline; I'm not even sure 100% gasoline is available here.

Years ago when I had a 1981 VW Rabbit, it would knock a little going up a particular hill when I used Meijer gas. Then one time I bought a tank of Shell gas, and it didn't knock or ping on that hill. That made a believer out of me.

 

I got 14 with 235/75's . Now have 31x10.5's, but I'm scared to check it.

 

Novaman, I also have a 2000 and I have almost the exact same MPG numbers as you. Interesting...
Higher flow air intake maybe gave it 1 MPG increase on the highway.