It's my understanding that going up a grade won't hurt, eg: 5w-30 to 10w-30, or say 10w-30 to a 10w-40. I've used GC 0w-30, Castrol 5w-40 and M1 0w-40 in the Z4.
I don't think it will hurt to use the MMO with either grade.
Supposedly Rislone helps with the tick. Like any kind of additive though, YMMV.
Pay a visit to the Pennzoil and Mobil websites. Mobil in paticular has lots of info.
Deltona Dave's point stands.