I have a 2004 chevy express van with 150000 miles. I’ve done a tune up about 10000 miles ago and air filter seems fine, but yet the gas mileage has gone down. What is going on with this car?
What do you mean Air Filter SEEMS fine. What test did you do? I don’t think it has anything to do with the air filter, but at 10,000 miles it may well be due for a new one. Check your owner’s manual and it should tell you how often each maintenance item needs to be done. Note: It will list both miles and time for most items. That is which ever comes first.
OK now about the fuel mileage. You are comparing what fuel mileage to what fuel mileage? Are you looking at what you got last May at 70? compared to last week in the snow storm? How are you measuring it? Over what time period has it gone down? Slowly since 2004 or just last week?
For most people visiting here, it is now winter and in winter most cars get lower mileage. It is caused by temperature, driving conditions and winter blended fuels.