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Old 04-26-2003, 12:10 PM
jcantor jcantor is offline
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Join Date: Jul 2002
Location: Trenton, NJ
Posts: 248
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).


'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)
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