lousy mileage on 2004 Ford Taurus

My miles per gallon has dropped from 19 or 20 mpg to 16 or 17 miless per gallon, why?

Asked by for the 2004 Ford Taurus
1 answer
I would check your basics, i.e. how are your tune up parts i.e. spark plugs, filters? Do you have a Service Engine Soon Light on ? This could mean that an engine sensor is not working properly which will really effect your mileage.