Hi All,

Without the availability of regular leaded fuel is it safe to use super unleaded with a 97 octane rating for my car? I've heard that problems could occur on the valve seats. Mine has a mechanical fuel injection. We also have regular unleaded with a 92 rating. What would be best? I run my car around 2000 miles a year.

Thanks,

Kevin

Hi Kevin,
Unleaded fuel won't hurt your car. All of the Mercedes gas engines have hardened valve seats. The only change M-B made when they produced engines for use with unleaded fuel was the addition of 2% tungsten to the seat's alloy. I've been running my 250SE, 3.5 and 6.3 on unleaded for 10 years with no problems. The original valve seat material seems to be just fine.
I would use the 97 octane variety when available. My stuff runs okay on 94 octane.
Regards,
Randy D.

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W.R.Durrance
ASE Master Tech
Mercedes Tech 19 Years

Hi Randy,

Thanks for your reply. I guess I'll start using the Super Unleaded with a 97 octane rating.

Kevin

Hi. I am negotiating for a 66 230sl and I never thought to ask the owner about the fuel he uses. By the previous posts in this thread, can I assume that I should just use the highest octane unleaded I can get? Is there a serious problem with using regular 87 octane? Also, was there such a thing as US spec vs. Euro spec with regards to the engine (compression ratio)?

Thanks,
Rodd

[This message has been edited by Rodd (edited 02-11-2000).]

Hi Rod,
Use the highest octane unleaded you can find. Around here that's 93 or 94 octane. The 87 octane would require retarding the ignition timing and may cause damage. The early SOHC sixes are noisy enough to mask the sounds associated with "pinging", so its best to use the appropriate octane fuel for the car.
There were no differences in US Vs. European engines in 1966, but some of the models were made to run on the poor quality fuel that was once a problem in North Africa. So there were "low compression" engines built for these specific markets.
Regards,
Randy D.

------------------
W.R.Durrance
ASE Master Tech
Mercedes Tech 19 Years

The compression specs. are stamped on the head in the casting #.
This is located on the head,drivers side, above and 1 inch back from the # 2 spark plug, at the seating line for the valve cover.
The last 2 digits will be the compression Ratio. 9:5 is the standard ratio.