Read the first link carefully then choose any of these three excellent oils below from any circle track race parts distributor.
However, you can now get Valvoline Racing Synthetic 20-50 at nearly any auto parts store for about $4.50 qt. It has as much Zink additives as the more expensive ones. I use it in my 600 hp alcohol dirt circle track modified at 8,000 rpm... and this $15K engine runs cooler than any other I've had before.
http://www.abcauto.com/MessageCenter...?ContentID=162
http://www.bradpennracing.com/
http://www.joegibbsracingoil.com/
http://www.championbrands.com/SpecSheet/EOXP.pdf