Conversion to Unleaded

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Dan Berry

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Can anyone help in offering advice or comment in relation to converting my 1976 450 SLC from leaded to unleaded petrol ?  I have had various conversations with mercedes mechanics, some of whom state that I should just start using unleaded and "it will probably be OK", to others who think that I need to spend £750 on a conversion (although I am not sure what that entails).  Any help would be much appreciated !
 

Andy

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Hi Dan,

Have a look through the pages of this forum. There is plenty there on this subject. Personally I would  listen to your mechanic and just run it on unleaded. Or remove the heads and have the seats changed if you got plenty of money to blow. But before you do any thing. Read the comments on the previous pages

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Andy @ www.mercedesservicing.com
 
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Dan Berry

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Andy
Thanks for the advice.  I have seen the previous forum topic on unleaded fuel. I have a couple of questions !!
If I start using unleaded should I use super unleaded ?
What sort of additive should you use with it (and where can you get it from) ?
How do you know if the engine is not taking to the unleaded fuel.  The 450 has a V8 and I presume that if the vlave does go then it would be a costly job.
Also (and apologies for my general ignorance here !) but what is LRP and what is the effect of using that ?

Sorry for all the questions but am trying to work out if it is cost efficient to start using unleaded or not.  I only travel around 6000 miles per year but am already concerned about the impressively high fuel consumption that I am getting !

Thanks again for all the advice Andy.
Dan
 

Andy

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Hi Dan,

All the fuels are effectively unleaded these days. LRP (Lead replacement petrol). It was the lead that lube the valve seats and stoped them burning out. The fuel to use is the fuel with the highest octane rating as this will give you the best burn. Which I think may well be super unleaded. Thats why its more expensive. Many motor factors can supply you with octane boosters and lead replacement additives etc. Whether I would bother is another question. The 450 did 20mpg at the best anyway. So use this as a guide and experiment yourself.

As I have said in previous forum q&a, its a bit like russion roullette. You may burn a valve out. You may not. Its not cut and dried. MB did have a list stating which engines where fitted with hardned valve seats. The dealers won't tell you. Not because they are stubborn. More because its too much hassle. I must say I wouldn't bother either. Too find the info would take probably over an hour to find. When I and the dealers are busy working on more immediate matters. I know it sounds callous. But that the way it is.

I would just drive the SLC and enjoy it. If it burns out a valve (taking into account IF) then sort it then. Either way its not going to happen over night.

Regards
Andy @www.mercedesservicing.com
 
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