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.)

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99 E300 133K
98 ML320 99K
87 Saab 900 Turbo Conv 123K

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

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Jeff

'87 560SEL 267K (177K on motor) Blue/Blue
'98 Buick LeSebre 60K (wife's car)
'56 Imperial Sedan 124K
Past Cars:
'67 Dodge Monaco 130K (Sold)
'87 Chrysler 5th Ave 245K and going strong (sold)
'73 Plymouth Satillite 175K (sold)
'96 Chrysler LHS 80K (totaled)

Jay,

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

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Steve
'93 400E