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Q: Has 135000 miles on original spark plugs. Car runs smooth and averages 23 mpg. It's hard for me to fix it if it ain't broke.

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Should I have the car tuned anyway and if so, what's the cost?

Spark plugs are replaced on a manufacturer specified maintenance schedule, in part due to plug gap erosion. Regular replacement at the 90,000 mile service interval interval that is specified for you model year also prevents a circumstance where the plug threads seize in the engine head. With regard to plug wear (gap erosion), inasmuch as you are fully 50% past the recommended service interval for the plugs, the gap is likely greater than the factory spec. That means the "plug is broke" because out of spec gap means the combustion in the cylinder is going to be less than optimal, the engine will be more subject to intermittent (indeed undetected) misfires and all that puts a burden on other vehicle components for example the catalytic converter in the case of misfiring. If you desire to schedule spark plug replacement on your vehicle, please simply request spark plug replacement service. The responding certified mechanic will get this fully addressed and, while at your location, will also be in a position to answer any and all other maintenance schedule questions you might have regarding your vehicle. Please don’t hesitate to follow-up with any additional questions and concerns that you might have as we are always here to help you.

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