Multigrade
I have been running two Lycoming O-235's and two O-360's on Shell multigrade, the O-360 run just fine on it.
Both the O-253's have had problems with the Piston pin plugs being " bacon sliced" by big ridges that have appeared in the cylinder at the place that the rings stop at the bottom of the cylinder.
I am now running the O-235's on Shell 80+ or 100+ depending on the season, the problems have yet to reappear, it is a LITTLE EARLY to be conclusive about this but it seems that the O-235 MAY NOT like multigrade oil.