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Bad gas mileage

1967 6
I am getting really bad gas mileage on my 2003 X5 we have changed the plugs, wires, filters, used lucas in the gas cleaned the throttle body any ideas on what else it could be?
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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

regular 89 i think
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
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