They are definitely compatible. I'm going back to conventional oil as soon as the weather warms up again. Mobile 1 has served me well with cleaning out the passages for the cam bearings, but it tends to find its way thru mated surfaces of older engines such as my '77 M110. Back then, engines weren't made with today's closer tolerances. If you do switch back, I suggest letting the oil drain over night to get as much out as possible. This is, of course, starting at operating temp.

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