How often should sparkplugs be changed?
In a lawnmower? When the plug shows wear when inspected for the season. In a vehicle? Depends on the vehicle and how it’s driven.
Also depends on the type of plugs. Standard copper plugs about 30k miles. Platinum can go over 50k miles. Iridium can go to 100k miles.
Um…perhaps your owner’s manual maintenance schedule would know the answer?
If the car is 10 years old or less, it came with plugs that should last at least 50,000 miles. If you put in the same plugs it came with, expect another 50k
I would hesitate to leave plugs in for 100k miles, no matter how good they are, because plugs that stay in that long have a nasty tendency to not want to come out. 50k miles is a nice safe distance for platinum or better plugs.