I really need some help I have 88 xj it's gettingg really bad gas mpg 8to 9mpg not lifted idk y the hell it's that bad it should get 15 to 16 right???

 

If the engine, drivetrain, and emissions system are operating near optimal efficiency?

What is....
the year?
motor?
last time a tune up was performed?
kind of gas/octane rating?

How...
does it run?
is it driven?

 

4.0 inline six 140000 muffler cut short 87 octane I drive it normal the weird part is it gets better mpg off road then on road?

 

88 leaks oil over top of valve cover I love it just pissin me off lately sucking the heck out of some gas and oil leak b

 

What about the tune-up as already asked?

How are you calculating your mileage?

 

Check your vacuum line from the MAP sensor to the throttle body. Mine was broken right at the throttle body so it looked OK until you tugged on it. If that vacuum line is not secure, you will get terrible gas milage.