How do you know when to change the spark plugs

Remove a spark plug and look at the small metal tip surrounded by the porcelin insulator if the tip looks rounded that indicates a worn plug, also over time the gap will increase because of wear. Obtain a spark plug gapper and check to see what the reading or gap is and then compare it with what the recommended gap for the car is, if the gap is cosiderably larger on the old plug replace the spark plugs.

Check spark plugs every 30,000 miles or 24months.Which ever comes first.Normal wear on the tip of the plug is a brownish to greyish tan color.Anything else may indicate another problem that should be checked out

Its best to change your spark plugs every 30 to 60 thousand miles.