Spark plugs were changed at about 10,000 mile intervals. The arrival of plugs made with special metals such as platignum tips, or irridium, has extended the interval to as much as 60,000 miles. You need to check which type of plugs are fitted to any car, as standard plugs could have been used instead of the longer life ones. The handbook will usually recommend which type to use.
go by the recommended mileage in the scheduled maintanence section of the owner's manual.
Change the plugs and plug wires at around 100,000 miles or earlier if you detect a miss or loss in performance of mileage.
Recommended change is 100,000 miles
recommended to change at 50 thousand km's
when do you change spark plugs
Whatever is recommended in the owners' manual will be your best bet overall.
you can get upto 100,000 miles on a set of plugs
Change them at 100,000 miles or sooner if you experience poor performance or poor fuel mileage.
Only if there's something wrong with your old spark plugs.
It is recommended every 30,000 miles.
NGK platinum plugs
To change the spark plugs in a 1997 astro van do I have to change the spark plugs from the bottom of the engine/