A question for old timers. My M119.982 engine is pushing 172K. As the cylinders are accumulating carbon, thereby raising compression, would you place a colder spark plug to counteract any chance of pre-ignition?

Best place to start would be to read the plugs, but I don't have spark plugs that i can read right now, because they're all fouled up due to top engine cleaning.

But, as a general rule, should you go colder plugs as the engine gets more miles?

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