Have been using GC or M1 15W50 in my mowers for years but I don't see the temp chart in my Toro TimeMaster's manual. It has a B&S 190cc engine and it looks like they only want the 30W, can I get away with one of my many multi weights syns in the the hot weather? Is there a synthetic 30W that is locally available, I can't find one, if not what is the best 30W to use?