ok thanks.
the part that i find hard to understand is: if 20w40 is ok, what would be the disadvantage of a 20w50? because as i understand, both are made to support a certain temperature range, and both start at 20. so for the cold part of the range i assume they would be the same, only the one going up to 50 can take more heat at the high end.
but i admit i'm a laymen when it comes to the science of oils so please correct me if i'm wrong.