XJ Fuel Mileage Help

[N-Smooth]

When I would drive my XJ to Moab with 33's and stock 3.55's I'd get as good as 17 on the stretch from WJ to Wellington and that's going 5-7 over the posted speed limit the whole way. Sometimes I left it out of OD even...

 

[ozzy702]

Given everything you guys are saying there is definetely something wrong with this XJ. I'll dig into it this weekend and see what I can come up with.

With as many miles on it should I also be looking at water and oil pumps for this thing? Anything else I should do?

 

[XJEEPER]

I have 187k miles on my 2000 XJ, with the original oil pump and still have 45-50 psi. Water pumps go out like any on other belt driven water pump. Your mileage is definitely low, tune up and fluids/t-stat change is always good on a rig which you lack the maintenance history.

Pretty sure the factory T-stat is 195*, running a colder Tstat than stock in the 4.0L will reduce mileage because the computer will stay in open loop and be delivering more fuel that needed.......which long-term can also damage the cat.

I average 17 mpg on the freeway with 4:88 gears, 6" lift and 285/75/16 tires, FWIW.