Should spark plug gap be changed lower or higher for higher mileage vehicles?

My Benz has over 240k. I've gapped the plugs to oem spec can't remember right now, but should I reduce or increase gap due to the high mileage it has? I'm asking due to the fact that by now the car must have some wear there for the compression may not be the same anymore due to wear and tear on the rings and valves.


The basic answer is, you need to gap it to spec. The reasoning here is the ignition system is designed to run at the spec'd gap. Running it narrower will cause it to get poorer fuel burn and thus poorer power and fuel mileage. If wider, it becomes harder on the ignition system. Considering most, if not all of the ignition parts, are as old as the car itself, putting them under further stress will cause them to fail sooner.

There's really no good reason to gap them at anything other than the stock spec. Overall, the wear on the engine will not affect it one way or the other.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.