Curiosity...same here, been thinking about adding it before an oil change but the engine runs great and doesn't use oil w/193k miles. I think I'm going to leave it alone.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I'm with you, when it's running good, leave it alone.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).