Spending a few hours (or days) over at Rx7club reading all the oil threads there will put you light years ahead of any advice you are going to get here (no offense to anyone here!). Plenty of real-world experience on that forum, lots of rotary fanatics and rebuilders that have enough experience inside them to see what oils work well and which ones dont.
The only difference I have personally seen, between the ones I have owned and torn down, and the engines of other peoples Rx's, is the ones that blocked off the factory metering pump and ran a 2-cycle premix had significantly less carbon building up on the rotor faces versus those who just left the metering pump in place.
The early carb'd 12A's were pretty solid, the later 13B's were decent but seemed to let go earlier than the 12A's, and the 13B single and twin turbos.... once you get up around 100k miles, seems like you are seriously on borrowed time. You will see occasional exceptions to that, of course. I managed to get my last single turbo to 125k miles before it blew, and I was pretty happy at that. The post-mortem showed a little bit of carbon on the rotor faces, but the apex seal channels and side seals looked great. This was on years of whatever generic 10w-40 or 20w-50 I had in my stash at the time. Havoline, Valvoline, Mobil, whatever.
You'd probably be better off not being too concerned about what brand of oil to use, and better served stashing a few extra $10's and $20's into a piggy bank every week to help offset the cost of the inevitable rebuild you will be facing after a few years. Its going to happen. In the meantime, enjoy the hands-down funnest car you will ever own. Finding a 93-95 Rx7 around here that hasnt been seriously abused or teenage-mod'd to Hades and back is getting a bid hard to do.....
