if your crankcase is vented (like all the flatheads) there is no moisture or methanol in your oil. the engine and oil are too hot for either of those two to exist. methanol's ability to mix with PAG oil or changing flathead oil often because it has methanol in it is a wives tale. you need to change your oil because these motors have no oil filter and only hold 12-14 oz of oil
Twice this morning I'll take exception....and I usually agree with your posts! LOL
Run a Tillotson carb on a flathead (limited, or other) and you
WILL get methanol in the crankcase in very short order.
Idling a flathead with a Tilly on the grid is probably the worst thing you can do for it.
In fact, any carb that is tuned rich for bottom end, especially on a flathead, will put fuel into the oil. From purple plates to stock appearings, .059" jet and up will dump fuel in the cylinder; couple with low tension rings, larger cylinder clearance, and slow timing, you will get fuel past the rings. Then consider that most are mounted on a 15* motor mount...When you shut the engine off, that fuel puddles at the floor of the IN port and gets past the valve guide as well.
As for oil temps, we see very cool oil temps in flatheads, especially compared to big engines.
Changing oil due to fuel contamination is definitely NOT an old wives tale.
Another reason to change the oil often is having no oil filter - to that, I most certainly agree.
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Brian Carlson
Carlson Racing Engines
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