I have always used Mobil 1 20-50W Syn. in my 99 Bosch HSE 156K, but used 10-30W about 3 weeks ago. Now I am having dry starts after about 4-5 hours of sitting. Would that little of a difference in wt. make her do that? I changed wt because of cold weather coming. Should I dump the oil and go back to 20-50W?