My m18 and m20 kohler horizontal twins cant use a 10 30 oil. They knock and the low pressure oil light stays on. Commercial simplicity tractors are 12 to 18 thousand each. So i am not destroying them for a test ..So do mine, among other choices.
That being said, SAE 30 oil is getting harder to find and not available in synthetic. There are plenty of choices in 10w-30 synthetic as well as RT6 in 15w-40. B&S also recommends 15w-50 synthetic for commercial use, and that is available in Mobil 1. 15w-40 RT6 seems like a good choice to me. When purchased by the gallon it's about the same or even less cost that a conventional SAE 30.
Maybe i should stock up more straight 30 ?? Good idea ?