Why is it so expensive?
How often do spark plugs need replacing? on 2006 Mitsubishi Endeavor
Mitsubishi recommends replacing the spark plugs every 30,000 miles. The reason the expense is so high on your vehicle is due to the labor cost. It takes over 2 hours to replace the spark plugs on your Endeavor.
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try iridium plugs they are expensive but last 3 times as much