: 2002 Deville poor gas mileage

Sam Mize
05-19-04, 09:15 PM
I have a 2002 that was great on mileage until about 6 months ago there was a factory recall to replace a fuel sensor. Since then my mileage has dropped about 4 to 5 miles per gallon. I've taken my car back to the dealer several times and they say there is nothing wrong. How can I get this corrected. The car has 25,000 miles on it.

05-19-04, 10:26 PM
Are you basing the fuel economy comparison on the electronic AVG MPG or on actual fill data at the pump??

Any changes in your driving style or schedule...?? Just a little more city driving can dramatically affect the average.

One thing to do is to fill the tank and reset the electronic data on the fuel data center. Run thru several tanks of fuel and keep records of the fuel added. Fill the tank at the same station and pump in the same manner to compute the total fuel used and actual average MPG. Compare this to the electronic data over this same time period. If the numbers match closely then the system is probably working correctly and the change in fuel economy would more likely be attributed to driving schedule, weather, tires, brakes, etc.... If the numbers do NOT match closely then it is an indication that unmetered fuel is entering the system and would indicate a problem that can be diagnosed. Something like the fuel pressure regulator could be seeping fuel internally and causing rich operation due to the unmetered fuel entering the system. This would show up in differences in the actual vs. electronic MPG.

Any change in tires or tire inflation? Different tires/low pressure can cause dramatic changes in fuel economy also.