dhreeves

My 2004 1.8t is getting terrible gas mileage. It is completely stock and the last few tanks I am getting 16.x mpg. I have no cel, brand new tires with correct pressure in them. I have done a TON of research on here and based on it I have done the below but it has not made a difference. I have an OBDII reader and have no codes but I do not have a Vagcom.

fuel filter
air filter
spark plugs
MAF cleaned
IAT cleaned
suction jet pump (was also having very firm brake pedal)
3 way check valve on top of sjp
2 way check valve below sjp
2 way check valve near air box
seafoam in crankcase, fuel, intake
diverter valve (was getting turbo underboost code)
02 sensor

I have tested the PCV valve by removing the oil filler cap and dipstick while it is running but there on no suction on either so it doesnt seem like a PCV valve. Also there is no noticeable noise that would indicate a vacuum leak, no noise at all from the PRV valve.

pearlwhitesix

Is this mainly city stop and go driving or mixed? I average 23 on 75% highway driving. I have a 5 speed manual. These cars aren't as good on gas as people might think.

replayrnaudia4

Could be the winter mix of the fuel your buying. Winter fuels generally have more ethanol in them so your milage will drop. My average always drops in the winter months.