I was doing a job at the Lancaster Pa. Post Office maintaince building the other week and asked the mechanic what oil they used. Yup,15-40 recycled oil All Year Round. He was working on a cylinder head that dropped a seat. The head internals were shiny-bright with zero varnish. Understand, this was the only engine there I actually looked at but it sure was clean inside. I know a lot of large fleets use recycled oil, but was a little suprised they did'nt run 10-30 for the winter. It must be working for them. My 92 Astro van likes 15-40 in the summer,but definitely likes 5-30 in the winter.