I have heard that as the 2F wears, some people go with 20W50 oil. Wondering if it's time for me, here's the details of the engine... - 2F from a '79, about 150,000 miles on it (the last 50,000 have been on road and highway). - It has never been rebuilt. - It does blow oil (suspect that it's coming from the head from the results of a compression test. - I never take the engine above 3,000 rpm. - I have noticed a rattling between 2500 - 3000 rpm under load. - I have adjusted the valves in the last few weeks (they did not need a lot of adjustment). When I took the cover off, and ran the engine, I did not see a lot of oil flow from the rocker assembly. The top of the head was not dry, but I didn't know if I should be "seeing" a lot of oil movement. - I live in Michigan: Summers are around 90 degrees. - I have been using 10W-40 oil in it since I bought it 50,000 miles ago. Will the 20W-50 help quiet the rattling that I hear? I'm not too sure about what may be going on with the internal parts. My main concern is that rattling that sounds like it could be the push rods but I'm not sure. :dunno: Any thoughts?