I have a 90 GXL, 60k on a rebuilt engine. I recently changed the spark plugs and the fuel filter, and ive noticed i now get bad gas mileage, around 14 mpg. Before i would get 18-20 mpg. Last night, after getting home i checked the fuel filter connections while the engine was running, and everything looked dry, no leaks. The spark plugs were were NGK BUR9EQ, BUR7EQ from Advance Auto Parts. The first week after, i got 14 mpg, and i figured it was because of the gas wasted when removing the fuel filer, but now it is 14 mpg again, after i filled up the tank. Any ideas what could cause the worse gas mileage?

 

Make sure all your spark plug wires are on fully. One plug not firing might not be noticeable in drivability, but it would alter your fuel economy.

-=Russ=-