This depends on the type of spark plugs that are in your car. Older cars (15-20 years old) are more likely to have standard plugs and they last 12,000-15,000 miles, newer models up to the year 2000 are platinum tipped and will last 30,000 miles. Some 2000 and newer have iridium tipped plugs and will go 90,000 to 100,000 miles.