How do I know when to change the spark plugs on in my car?

I just bought a 1999 Subaru Impreza Outback Sport (its a mouth full!) about five months ago, and I was wondering since I have no idea what the previous owner had done for maintenance, how do I know I should change the spark plugs?How do I know when to change the spark plugs on in my car?
What he said.......you should change your plugs every 70,000 miles or so. And I believe on a Subaru it's a boxer type engine so they're probably pretty easy to change out....i would recommend Bosch Platinum +4's because you don't have to gap them....just screw them in and go. Hope this helps.How do I know when to change the spark plugs on in my car?
When in doubt, change it out.
Usually you can get about 100,000 miles on them before they need changing. It's 9 years old and probably close to 100K. Spend the $20 for new plugs. Also, if it doesn't already have synthetic oil in it I would switch to full synthetic and a new filter. As so as the oil starts to turn dark it's time to change the filter. Don't change the oil as synthetic will outlast the life of the vehicle.



The car should last you a long long while
anytime you buy or trade for one like that its best to just go ahead and change everything and make a record of it ,then you know when it was done,the previous owners may not have changed those in a while so i would go ahead and give the car a tune up,and then you,ll have accurate records of when it was done,i always do,and never have any problems from most of my trades,they should be changed about every 30 thousand miles,but unless you got a real good maintenance record with the car id go ahead and tune it up real good ,change all your filters and check all the belts,anything that could cause future problems that looks bad id go ahead and change it now,it may save time and money later on ,good luck with it.
if da car trembles but change them anyways your gas milage will go up
they arnt hard or pricey go ahead and do it.