OK, I did not know the 850 motor had knock sensors, thats good info. I'm going to run a few tankfuls of regular and see what happens.

The only modern vehicle I've owned that gas grade made a really dramatic difference in was my '95 Jeep Wrangler. I had the 4.0 liter straight 6, which is a pretty unsophisticated yet bulletproof engine, and has been in production for close to 30 years I believe. Anyway, no knock sensors, no ignition retard ability, nothing. I got stuck once or twice where I was close to empty and the station I found had only regular. Man, that motor knocked so loud I thought it was gonna fall out. My vintage iron I always run premium. I have a habit of rebuilding engines with higher than stock compression, don't know why and I can't seem to get it to stop....