I'm not sure what he uses in his Honda or FC (if he still has them) but he has never owned an RX-8. Just run a good 5W-40 or 0W-40 and you will be good. If money is a concern, then Rotella T6 5W-40 is probably your best bet. But more importantly than the brand is that it is changed often and that you check your oil level during fillups and add oil as needed. As for "weight", I would not run less than 5W-30 and why do that when you can run a good 40 or 50. In Texas the first number is not really important.

 

I use 5w30 year round in Texas. Might be better going up to 40 in the hot hot summer months but tbh I would have no idea and don't pretend to know what's good or what isn't. If my engine ever blows up I will be sure to report my experiences here.