Sudden reduction in MPG
 

Hi, I'm new to the forum and have a fuel economy issue I really need help with.

Car in question is a 2002 Chevy Venture van, with 200,000 miles on the od. I have kept careful records in the 90,000 miles I have owned the car and it has averaged 21 to 22 mpg (combined city/highway) and 25 to 27 mpg highway.Better in winter than summer of course.

Recently (and rather suddenly), both in town and highway mileage has dropped about 3 mpg.There is no question about this as I have an ultra gage and a OEM in car mpg computer and both are backed up by manual calculations.

New plugs, new oxygen sensor, new air filter, new gas filter, same gas station, same air pressure in the tires (40 psi) ..... and nothing has made a bit of difference. It has been very warm here (mid 90's) but that happens every year (just a little later).

Can anybody tell me where to look next ?

Where are you located? Could your stations have switched to E10 from straight gas?

Running your A/C?

I would say a small decrease like that is normal, if it had dropped by 10 MPG, I would be more concerned. There is a 7 Mpg difference between my best tank and worse, there are so many things that affect mpg, I doubt youre driving style alone would remain consistent enough to keep the same figure.

Thanks guys for all your replies.
I always use the same station and they only have E10. If they had switched to straight gas my mileage would have improved.
When I run the AC I get about 0.5 mpg drop. Nowhere near enough to account for my 3 mpg drop. If I compare summer mpg with previous summers I still get a 3 mpg drop.
At each fillup I record gallons, miles, the ultra guagempg estimate and the car computer mpg estimate and compare them all over time. I could probably notice a drop in mpg of as little as 0.5 mpg over time. A 3 mpg drop is huge! Almost 15%.
I'm convinced its related to failure of some engine component and yet I'm not throwing any codes.
I'll be driving from Florida to Colorado in a week and the loss of mpg works out to $80 more in gas.

Have you checked your brakes?
Perhaps one or more are now dragging on the rotor.

Might be a silly comment, not sure how the weather systems work over there, but over here in the summer the wind changes direction bringing warmer air from the south. If the same happened there, you could be heading into a slight headwind without knowing, and missing a tailwind which in a boxy Van could make a difference.

I second this suggestion.

Also, how many tankfuls have you been experciencing your 3mpg loss?