LISTEN UP!!!!
M1, do you really mean that you heard of switching to MINERAL oil for winter, or do you just mean STRAIGHT WEIGHT versus MULTI-GRADE?
AND.....get it right supercub 37! Unless alot has changed since the election, "...straight mineral oil 30W..." doesn't exist. A "W" preceding the weight means "ashless-dispersant" oil. Mineral oil is NOT "ashless-dispersant", and is most-commonly used as a break-in oil.
I do agree with your filter and oil change interval recommendation.
I'm guessing you guys just made some typo's, right?
By-the-way. I'm a straight-weight user, and recommend it for everyone.
With our temperature ranges, W100 (SAE 50 weight, ashless-dispersant) for summer. And W80 (SAE 40 weight, ashles-dispersant) for winter. For colder periods or areas, W65 (SAE 30 weight, ashless dispersant).
For break-in....manufacturers recommendation, or overhaulers recomedations, when a warranty is at risk.
Otherwise, for break-in, mineral oil until consumption has stabilized, then straight weight ashless-dispersant suitable for the temps.
In Anchorage, we could probably get away with straight-weight ashless-dispersant SAE 40, year-round, in Cubs. But Beaver's and the 6-cylinder Cessnas should run 50 weight for summer.
Check your engine manufacturer or builders recomendations, and stick with them. You don't need to second-guess the guy you trusted to build that thing.
Dave Calkins.