multi-viscosity synthetic oil

The engine in my 31 year old Craftsman riding mower with a Tecumseh OHV-125-203015A engine calls for SAE 30 wt oil above 32° and 5w30 below 32°, then the manual reads, “Although multi-viscosity oils (5W30, 10W30,etc) improve starting in cold weather , these multi-viscosity oils will result in...