What is the recommended mileage for spark plugs change?

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.