(quoted from post at 14:54:53 12/07/18) NO problem
I would go full synthetic like AMSOIL or stay with what you have. not much point in synthetic blends in my opinion. how "semi-" is it 5% synthetic 10% 2%?? 50% ??? it still counts as "semi-" or "Blend" at 1% technically
you'll be amazed how much better they crank over in the cold with synthetics.
Note: you will want to keep an eye on the oil pressure. a good thing about synthetics is they will clean your engine. the down side to that is the gunk and dirt will end up in your filter (were it belongs). no problem just keep and eye on the oil pressure and put a new filter on part way between oil changes if there seems to be any issue. of course that depends on how many hours you put on it. if you have good seals you should not have an issue with leaks. if you do have leaks after switching to synthetics its probably due to bad seals the the dirt was the holding the oil in
the older pre 1960 hemp seals are NOT compatible with synthetics and could leak. but if its from the 1970s you should be fine.
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