2000 gmc jimmy what would cause poor gas mileage problems?
Dirty air cleaner, injecters need replaced or cleaned, plugged fuel filter,replace spark plugs. A complete systems check for emissions. Transfer case locked in r
Low tire pressure.
A bad thermostat can cause a decrease in gas mileage. If the thermostat is stuck open, the engine will tend to run cold. Not only will this result in a perpetually low temperature gauge reading and poorly performing heater. It will also cause the ECU to richen the mixture, since the engine will appear to be warming up to the ECU. This will result in poor gas mileage. Replacing the thermostat will allow the engine…