Great technical info and I thank all for the diatribe. I have but one comment....switch to a diesel (then enjoy the diesel additive debates.) :)

Just for reference, I've been using 87 in my '87 560SEL for over a year now with no problems. When I first got the car I ran several tanks of premium before switching to compare performance and fuel economy. Without a dyno and/or a stop watch, I doubt anyone could notice a difference in performance. The fuel economy was marginally better (about 3-5%). Given the 15-20% difference in price between 87 octane and 92, my wallet comes out way ahead on 87 octane.

Several years ago, I tried experimenting by advancing timing on a '73 Plymouth until I was just below the detonation point with premium and compared this to running the same car at factory tune and regular. Since this engine had a somewhat lower compression ratio than the MB (8.5 vs 9.0 or 9.2) there was a more significant difference in fuel economy but STILL not enough to make up for the premium price.

Therefore the ONLY car that I run on premium is my '67 Dodge with 10:1 compression. Even so, I have to run the car slightly detuned especially since about 1/3 of the time the premium gas I end up with is definately NOT premium octane (ie the gas station cheats).

jlc

Re: All I really want to know is????
 

Jay,

Do yourself and your car a favor: call 1-800-FOR MERC and order an owner's manual. They've got 'em!