Leaded or unleaded

[kvz2000]

Hi,
Old topic I'm sure but need confirmation , I have a 1973 W114 280e , just spoken to a previous owner that said he used lead additive , yet there are so many contrasting views out there . I was told that all post war mercedes engines had hardened valve seats so do not require any additive!! And that this has been confirmed by Mercedes.
Yet on any search I do on mercedes forums I read of many owners that add a lead replacement or owners that have had hardened valve seats fitted ??
Very confusing and I would like to see if mercedes have made any statement on this . America say they have been using unleaded fuel since the early 70's and all there cars were manufactured to run on unleaded ,mercedes included ,if they were making unleaded engines for America would they really make a different engine for Europe ??

 

[219]

There was a list published in The Mercedes-Benz Club Gazette some time back , outlining which engines needed leaded petrol and which didn't .

It was not universal and the changes came around the time of your car , in some cases from certain engine numbers .

I'd advise you to write to the Classic Centre in Stuttgart , enclosing a photocopy of your registration document ( required by law there due to their equivalent of data protection act ) and they will give you a definitive answer for your particular car .

When I ran my W114 280E , SMS690N , back then , leaded petrol was still widely available and that was what I used .

 

[jaymanek]

I have always used unleaded in all post mid 60's mercedes.

In my 1969 pagoda I use Millers lead replacement/ octane booster aditive.. Cant do any harm but I dont think its required.
Well I know its not required as I have rebuilt the head anyway.

 

[Delayed Steve]

I think if your engine was sold in the US then it will be ok especially if it has a alloy head.
I've got a 73 Triumph and that was built for unleaded petrol .

 

[219]

I'd need to go trawling back through dusty piles of Gazettes , but there was an article listing which cars were OK and which were not ( and some changed mid run with engine/chassis numbers being quoted ) .

The changes would have been around the time of unleaded being introduced ( 1970's ) .

Earlier cars would not have been designed for the stuff as it hadn't been introduced . Having said that , it takes a long time to do damage and I ran my Ponton throughout the 1980's on a mixture of leaded and unleaded , depending on which pump I pulled up to in some cases - it never seemed to do any harm , and most folks reckoned even 1 tank in 4 of leaded was enough to avoid problems .

Ironically , properly old cars ( pre war ) are fine with unleaded since tetra ethyl lead being added to petrol only really started in the fifties to boost octane ratings - earlier stuff was the equivalent of two star .