couple years ago I was getting 20.7mpg in the summer and 18+ in the winter. Now I'm getting 19.3mpg in the summer. I have 74000+ miles on the car. Do I need to change the plugs? Never have done on this car. Any other ideas?
couple years ago I was getting 20.7mpg in the summer and 18+ in the winter. Now I'm getting 19.3mpg in the summer. I have 74000+ miles on the car. Do I need to change the plugs? Never have done on this car. Any other ideas?
It sounds as if you could use a complete tune-up. That's because it sounds like it hasn't ever been done and [not] because you calculated a 1 mpg difference in your fuel mileage after comparing after a couple of years. Hell, just a change in fuel formula over the course of a year is more than enough to drive outside of a 1 mpg tolerance.
Fuel Filter
Air Filter
plugs
wires
cap and rotor where it applies
Swap all the fluids
check seals for leaks, etc...
There's no cap and rotor on the '05+ GT engines. Agree with the rest though.
Also check the condition of the tires and tire pressures. Underinflated tires have more rolling resistance and can hurt gas mileage.