Many automotive SAE 30s, like the Valvoline Premium Conventonal I will be running in my van and truck this summer, are low on zddp. Not sure what the requirements are for lawn mowers, but I suspect the B&S oil has higher zddp levels. So the recommendation above to use an HDMO oil is good. But I would probably run Valvoline VR-1 Racing Oil (which comes in SAE 30, 40, 50, 60, 10w30, and 20w50), has nearly twice the zddp as modern SM automotive oils (and probably a good bit more zddp than current spec HDMO), and for a racing oil has detergents/dispersents making it fully sreetable for normal OCI.