Stock motors are all designed for 91 so I would not use it. I won't even buy 93 if I can buy a name brand 91.
Thanks for the replys. I use Seafoam once in awhile but I have never used Marvel Myster Oil. I have heard that its good to lube the top end of the motor. Maybe I'll just stay with Seafoam.
MMO has paraffin wax in it so I would not use it to lubricate the top end of the engine on a steady basis. A little MMO (1/2 ounce) now and then may be more helpful in lubricating the fuel pump.