This info is listed in your owner's manual. Don't have on the replace them at 75,000.
Toyota says to change at 30,000 mile intervals in order to maintain Emissions warranty.
EVERY 60K
The only ways to improve mileage are to check tire pressures, replace spark plugs, replace air filter, repair any causes for the check engine light to be on.....
700 bucks for drive belt, timing belt, vane pump belt and spark plugs.
Yes, you should replace the spark plugs in your Forester at the intervals recommended in your owner's manual.
Changing your spark plugs could theoretically make your car faster but not enough to make a noticeable difference. Changing your spark plugs when they are worn will increase your fuel mileage slightly.
If you have not done so, replace the plugs, plug wires, air filter, and fuel filter. Also replace all under hood vacuum lines.
you can get upto 100,000 miles on a set of plugs
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.
they probably did not space the plugs correctly and that can cause a loss in gas mileage and make the car act up.just replace the two plugs
It should make it run better and get better mileage after you replace the plugs with new ones. You may also want to replace the plug wires if the car has over 100,000 miles or is 10 years old.
There are six plugs. The front thee are under the coil packs on valve cover, rear are under the intake manifold, which has to be removed to replace the plugs. I suggest a qulified mechanic do the job, but for the D.I.Y. make sure to buy new intake gaskets. good luck. it is a pain.