SAE 30, 40 or 50?
 

Anyone run any of these in a rotary. Any reason not to, or reasons you would? Just curious.

Not really sure of the purpose of your question. Mazda recommends running multi-weight in every owner's manual and FSM that I've seen. That provides better startup, broad temperature range and overall protection than a straight weight oil can.

i've only heard of people running single-weight oils in race-only rotary engines. in the same breath, most rotary racecars that i'm aware of use multi-weight oils though. what exactly is you interest/concern?