Well, my car is a '93 and therefor N/A. My book recommends premium fuel (91 or better) but I've heard people say the N/A cars will run fine on the lower grades of gas. I really want to try this, I'd love to go back to buying regular and save a few bucks. However, if I had a turbo 850 I'd stay with the premium fuels. When you run the lower grades of gas your engine is more prone to knocking at lower levels of load than with the higher grade fuels. When you throw in higher levels of cylinder pressure (boost from a turbo or supercharger, or high compression pistons/heads in N/A cars) the motor will knock at even lower levels of load, and with more intensity, thus accelerating the possibility of engine damage. I've seen pictures of pistons that have been holed due to long duration driving under load and while the motor was knocking, not pretty. If your motor is modern, and has knock sensors, it has the ability to detect when that is happening and, on many newer cars, retard the timing on the fly to eliminate the knock. Most of the setups I've seen that can do this utilize distributorless ignition, but I'm sure a distributor can be made to do the same thing via vacuum advance/retard and interface with computer control. My wifes Jeep Grand Cherokee has this ability, it has fairly high compression (the HO 4.7 liter V8) but can run regular gas just fine because it has knock sensors and distributorless ignition, so the spark timing is variable through computer control and can be retarded if knock is detected. I don't think the 850 (at least the older ones) have either knock sensors or variable spark retard capability.