I just got my snow blower going after sitting in my garage for 8 years. I put a 5-30W Pennzoil oil in my crankcase. I was so happy that it started......It never crossed my mind to go with a synthetic oil like Mobil 1 or other How important is running a synthetic oil in a 26 year old Tecumseh 5 horsepower motor? Should I run the machine a few times then change over to synthetic? Should I just leave what I have in the crankcase Thanks!