Dude. There have been a zillion threads on premix & such. Don't start a new one.

Premix is running 2-cycle oil in the gas, usually after removing the stock oil injection system. Benefits include better engine lubrication, less carbon buildup, and removing all questions about what oil to use in the crankcase (if it's not being burned, it doesn't matter if you use synthetics).
Downsides include having to add 2-cycle oil each time you fill up, and possibly having your car gain that wonderful 2-cycle oil smell. It's really not bad, though I haven't had to fill up in the winter yet with premix.

-=Russ=-

 

as u heard from all these other owners its all about the love u give to the car
if u dont have it in you dont get the car, if u do u will have a lots of fun

 

On the Mobil1 issue; Even in a piston engine, if it is a high mileage/older engine, you typically do not want to switch to a synthetic. I forget the exact explanation, something about seals developing leaks, or piston rings? In any case, if it is a bad idea on a piston engine that has been running conventional oil for 100k+ miles, then it stands to reason it would be just as bad (if not worse from what I have read in my endless research) in a 7.

 

Yea, the reason for not switching to synthetic in piston engines are the valve seals. They are basically little pieces of rubber that seal the intake and exhaust runners from the oil in the cylinder head in an OHV engine. Regular dino-juice will make these seals swell up. After 70,000 miles and 5 years worth of thermal cycling, these seals will become permanently molded in their swollen state. Synthetic oils are not absorbed by the rubber, so as the dino juice slowly sqeezes itself out, it leaves little valleys and gaps for the oil to run through. That leads to leaks. I'm not too familiar with the seals on a rotary engine though. I've only had my 7 for a month now. Maybe someone else here knows whats going on.

 

I'm trying to think of any seals that would be affected by switching oil... the only thing I can come up with are the o-rings in the oil scraper rings, but I can't see those being affected terribly much - the metal & springs handle most of the scraping. If anything, you'd just burn a little oil, or have a bit more blowby into the oil system. The rest of the system should be fine, IMHO.

-=Russ=-