I own a 2006 Ford Escape. My car always gets 21-22 mpg in town or trips. We always use Valero gas. I live in Galveston, Texas and we took a trip to Boston last month and on the way there and back we got 25-26 mpg. We couldn’t find any Valero stations after Georgia and used mostly gas from Walmarts (Murphy Oil). Since we returned, we are only getting 15-16 mpg. I thought someone was stealing our gas so I bought a locking gas cap, but, we are still getting the crummy mpg. Did our auto computer adjust to the different atmospheric conditions or do we have a malfunction in our fuel system, like a bad sensor, etc.?

There are several things that might make your MPG go to pot. I doubt atmospheric conditions have anything to do with it. You probably never got over 1000’ ASL on the whole trip.

Have you checked the air filter?

Do you have an illuminated “check engine” light? If so, get it checked fro free at your local AutoZone.

There must be something else that you can tell us. If your estimate of reduced mpg is the only symptom then we tend to suspect there is nothing wrong with your car. You may have made a miscalculation or have based your estimate on too short a time span, one that included unusual driving conditions.

Since your car is still under warranty you can try bringing it to the Ford dealership. He may decide it simply needs some routine maintenance, but this would not be considered warranty work so you would be expected to pay for it.

My advice would be to give this more time to either work itself out, or for you to report additional symptoms that would help us with a diagnosis in the event there is a real problem.

Would the dealer do an actual MPG test of some sort? Or just check it for codes,maintiance on schedule and when both are OK say that all we are required to do.The dealer cant be required to prove a vehicle’s mileage or can they?

I do not know if any repair shop can perform an actual “mpg test,” whatever that is. And since every driver’s results can vary greatly, any such test is meaningless. A mechanic really can’t do much more than verify a vehicle is running normally, no codes and no emissions problems. If the owner is merely disappointed with his estimated mpg, based on his own calculations and driving methods, that is not the manufacturer’s problem.