You can come pretty close...30wt HDEO. Again, these motors were designed when 30 and 40 wts were the norm. Just about all of the "typical" oils (i.e. Castrol GTX, HD, Valv. Penn, etc.) are nothing like they were even 5 years ago. Also, my experience with 4 & 6cyl Porsche motors is that some of the multi visc. oils, when heat cycled a couple of times in a comparitively high-temp aircooled motor, tends to revert to it's original state (a 20-50 for example, tends to revert to a 20 wt, losing a good part of its viscosity additives.) If you haven't, go to Bob is the Oil Guy . com and check out the thousands of posts on this specific subject. You'll find that a substantial number of the posters prefer a very low viscosity multiweight in a performance, aircooled motor - even under track conditions. Now look at the cars they list as owning: Saturns, Toyota pickups, etc. Always easy to give "cutting edge" advice when someone else is out there picking up pieces of a fragmented motor. Bottom line is the choice is up to the individual owner. At the risk of being oldfashioned, I'll stick with a one-piece crankshaft.