2002 Ford Explorer Sport Trac XL 6 Cyl 4.0L
200,000 miles on original plugs. Still running good . Should I change?
Yes, go ahead and change the spark plugs. Even if running OK - no noticeable problems, there is risk of the spark plug threads corrosion over time - meaning the spark plug change possibly will involve cylinder head thread repair for damaged threads. Be sure when changing the spark plugs to place a small amount (one-two threads) of anti-sieze on the new spark plug threads.