yeah I ran 20W-50 VR1 valvoline racing oil in my truck for four straight summers, in my 235 in my truck and it never ran low on the preasure gauge unless it was really hot outside in summer, like 118 degrees here, and for those couple months I would use SAE straight 60 weight and it ran great, never spun a bearing, never thru a rod, in the winter 30 weight is probably good, but in the summer I would step up to either 15W-40, or 20W-50 so that the motor oil has the capability to adjust to the surrounding outside temperature demands and keep your motor safe, but depending on where you live and surrounding temp comditions determines a lot, I am not saying my statements are scientific law or anything, just saying it worked for me.
