Running on unleaded fuel

[Richard Smale]

I have read in Practical Classics that a lot of older SL's can run happily on unleaded fuel.  I use LRP in my 380SL (1981).  Is it best to continue using this, using unleaded or unleaded with substitute ?

Any advice appreciated.  

(Edited by Richard Smale at 9:31 pm on Jan. 19, 2001)

 

[steve]

Richard
Tables on this were produced by John Haynes and published by the Mercedes Benz Club .All cars before June 1981 will not run on unleaded ie have normal valve seat rings.Also it depends on the engine number  .According to the tables  on 380sl auto unleaded can be used on engine 116.962 from engine  number ending in 000021 onwards and from 6/81 date. Personally I use these tables in conjunction with an in line fuel catalyst to be on the safe side

 

[jim downie]

Sh*ll
's site reckons pre 1981 need new valve seats, 1981 - 1985 iffy, post 1985 Ok to use LRP or super unleaded.
However, I've been using Valvemaster + unleaded in my 1986 300TE (124) and I don't like the glazed residue on the plugs (although Valvemaster says not to worry).  Also there is no cost penalty using LRP v Valvemaster and unleaded.  LRP and super unleaded are 97RON, so the octane rating is OK, but does anyone have any bad experiences (rubber compatibility etc - steady!!) using LRP ?

 

[merky]

All R107 SLs will run on unleaded fuel

 

[Andy]

Richard
There is a lot of controversy regarding unleaded petrol. Should I use it or shouldn't. MB produced a list which detailed which engine had hardned valve seats & which did not. My experience of these after working on these vehicles for the past 23years is this.

If your really unlucky you may burn out an exhaust valve or two. Trouble is, it doesn't happen to every engine. The 280/110 engine seems a little more susceptable, but from experience a customer asked us to replace the valve seats on his 1983/84 280CE 123. We gladly took on the job. The head gaket had blown, and he thought it made sense to have the valve seats replaced at the same time. I duly ordered up the valve seats from MB. You can imagine my supprise when my machining engineer came back to me with the job done seats fitted. Telling me the old seats where harder than the ones that we were fitting.
Since then my thoughts are this. If you can use the red stuff then do. (Although its more green than red these days anyway) If you can use a good additive to boost the octane rating and it has chemicals to coat the valve seats. Then this won't hurt either.

But really it's a matter of bad luck if a valve goes anyway. For you it's double bad luck as V8, cylinder heads do not just fall off. If you have a 110engine 280 then again its a long expensive job. The later 4cyl 102 engines & 103 6cyl engines are not too bad. A days work should cover it if you just want the one blown valve replaced and nothing else.

To conclude then. If you don't do many miles then you would be very unlucky to burn a valve out. If you have acess to a good fuel additive then use it! But this still does not mean you will not burn any valves out!!!!

Hope I made a little sense. If not contact me on www.mercedesservicing.com

 

[Francois]

Steve,

Where can I find these tables? (which Merc club?)

Would this be the same for the 116.963 engines?

 

[Spencer]

I've already posted that I've been using a fuel additive, the firepowerpill, that has improved both the performance (more power) and eliminated the black smoke I was getting on starting the engine. My car is a 1980 380sl. As I have no mechanical knowledge whatever, I only started using this on a friend's recommendation, I would be interested to know if anyone else has tried it and what they think.

spencer