I drive a high mileage 73 VW, I started out using 15w-50 Mobil1 in it when I got it then changed to 10w-30 Mobil1 for the winter. I want to use just one oil year-round. would the 10w-30 be safe enough for summer use, or would the 15w-50 be a better choice?(summers here in SC are hot and winters rarely go below 20 degrees.) Second, I recently bought my daughter a Saturn SC2 with only 52,000 miles on it. Where in my area can I get a good engine cleaner? I'm currently useing Mobil drive clean oil in an effort to help with the cleaning process. I plan to use Mobil1 10w30 when I get the problem somewhat under control.Thanks for your help. ps this is a great web-site. I've been a mechanic for 30 years, and have learned more about oils in the pasttwo weeks than I ever knew before, Thanks to this site. .