I may take the time to test both fuels on my larger engines. I was tempted to buy the 20/20 blend but it's $15 more. Go figure. I don't see the point in paying $15 for 2% more oil. Since the 20/18 was the same price as the lower nitro. I decided to try it and I've used about four gallons this summer. I add a little castor and burn it in my 1/2 A engines. The biggest surprise for me was that the OS ran away from the Saito on a 9X6 but on the 10X6 any small mixture adjustment could likely make them equal. I would guess 13,100 RPM is getting into valve float range on the OS. In my opinion if you're going to run that kind of RPM you might as well use a two stroke. I assume the lower nitro effectively oils more due to the greater volume entering the larger needle valve opening.