How bad is the mileage?

Maybe 10 miles to a gallon

Ouch -what grade are you using?? s/b 91 or higher??

regular 89 i think

there's part of your problem - s/b using 91 or better

i recently bought a 2002 4.4i X5 and forgot and used 89 and got terrible milage and
performance from the engine - until i found out i should be using 91 or higher

thank God i only did it with 1 tankful - next tank i used 93

using 93 now as that's whats available and i get decent milage from it considering its a V8

try using the higher(est) grade available - not really much diff $$$ wise -especially in the long run -car will run better with less problems

sphelps2552 said:

regular 89 i think

Click to expand...

Doubtful that the gas brand or 'grade' is the cause of that "10 mpg", imo...unless it was an unlucky tank(s) of bad gas. The best mpg I see, over nearly 11 years & 86k miles is from 89 grade, with occasional 91/93, but my mpg doesn't vary much. If improving from "~10 mpg" to what should be considerably higher/'normal' was as simple as a few tanks of big brand name 93, it would be like magic, lol!

Some things that come to mind: fuel filter clogged, tire pressures very low, MAF sensor, exhaust or intake cam sensors, fuel injectors, etc. Hard to hand out a specific diagnosis, imo...

Have you scanned for any codes?
My 50Cts...
GL, mD