ondarvr, please don't take my comment wrong. All I am saying is people honestly have no idea of differences and therefore shouldn't be chastised for selecting the wrong type for their purpose. That's all! And IF the oil manufactures do add special additives to help with the increased heat in an air cooled engine, why make two different types? Why not use that same special oil additive in the TWC-3 oils as well. Sound fishy to me... I have used QuickSilver TWC-3 in all my 2-cycle lawn equipment over the years and still using them without issues as well... Just saying! :watermelon:
Again, it's not "better" ingredients, the the air cooled oils work better at higher RPMs, but can leave ash deposits in lower temperature, lower RPM water cooled outboards. On the other end, when you removed the ash creating ingredients the oils don't work as well at higher RPM's and higher temps. The oils still work well in lower temp, lower RPM applications though.
That's the condensed version of why there are two different oil formulations. Nothing fishy about it.
Chains saws, motorcycles and some other two strokes run at up to 12,000 to 13,000 RPMs, lawn equipment tends to run at much lower RPM's, so while one air cooled motor could run fine on TWC3 oil the next one may not. And like I said before, it's not every motor that's affected, only enough of them to cause concern and find the reason and solution.