Up here in Canada we use 10/30 oil in just about everything except the new car and truck which require 5/20 oil and if that oil is not used, the sensors pick up the difference in grade and shut the engine off.
Good grief!
I buy the 10/30 by the 55 gallon drum in Montana and it costs about $2.60 a quart with taxes and travel, Montana is 14 miles south of here, the oil retailer is another 100 miles south of the border. But in our flat tappet engines we add a product called "Trick flow", a 12 oz engine oil supplement and I cannot believe how slippery it makes the oil. So a basic oil change is $13 for the oil plus the filter and this Trick Flow is $14.95 but it really seems to make a difference. We use multi grade oils in our aircraft, 15/50 in the Continental engines, ( and my lawn mower as it too is air cooled) and Phillips 66, 25/60 multigrade in the radial engines. As far as oil filters we found that the heavier the filter the better.
We don't use Fram, ever. Genuine Ford/Motorcraft are the better ones or anything at CARQUEST. NAPA seems to sell from any manufacturer that has the cheapest build for that week. So we don't shop there either. I read here that some folks use 15/40 oil which is an excellent choice for running warmer temps.