How do platinum or after-market spark plugs affect gas mileage?

Answer by  Amber40 (24961)

Well the companies state that they will improve gas mileage. In most cases there is a small increase in gas mileage. I wouldn't expect more than about 5% improvement.

Answer by  meridian (466)

Platinum spark plugs keep the optimal spark gap much longer than copper spark plugs. There is anecdotal evidence that replacing them can increase your gas mileage between 8% and 10%. It is a general rule that anything maintaining your car in its best condition will improve the gas mileage of the car.