wd40 is good stuff, but not the best for after run oil, although it is better than nothing.

marvel mystery oil is a great after run oil. probably as good as any after run oil on the market.

twomanytoys is correct. there is an additive in sidewinder fuels that practically eliminates the need for any afterun oil. i switched from trinity race blend to sidewinder a few years back and the stuff is great. it tunes like the premium fuels such as byrons and odonnels which is really saying a lot.