I am not an expert but have recently purchased a 1982 w123 230E Auto.
There seemed to be much contradictory and confusing advice. I found an excellent article on the general use of Unleaded fuel here at http://www.pumaracing.co.uk/unlead01.htm. Here are some quotes:
There is no such thing as an engine where the valves and seats don't wear at all because these are after all heavily loaded components. What is really being asked here is "will the valve seats last an acceptable period of time on unleaded fuel?". The answer to that is really "acceptable to who?". It depends on the view about engine life that the OE manufacturer took in the first place.
Aluminium - Any modern aluminium head (let's say post 1975) will have inserts that are able to run on unleaded petrol, even when the OE manufacturer says it is unsuitable. What they mean by "unsuitable" is that they are unwilling to guarantee the same 200,000 mile or so service life that they would expect from a post 1989 engine. They do not mean that the engine will suddenly and immediately fail just because you run it on unleaded petrol. In practice it will have no impact on the average car owner at all given that very few people keep their cars that long. If you have an aluminium head from a major manufacturer (Ford, VW, Peugeot, Vauxhall, Fiat, BMW, Mercedes etc) then stop worrying and just run it on unleaded. The worst that can happen is that eventually, in 100,000 miles or so, the valve seats will have pitted enough to need recutting but by then the chances are that the rest of the engine will be worn out too. There is no way the inserts will just burn out though in the same way as can happen to plain cast iron.
The full article is there in the link above. I have contacted MB UK and they are getting back to me with the answer.
There seemed to be much contradictory and confusing advice. I found an excellent article on the general use of Unleaded fuel here at http://www.pumaracing.co.uk/unlead01.htm. Here are some quotes:
There is no such thing as an engine where the valves and seats don't wear at all because these are after all heavily loaded components. What is really being asked here is "will the valve seats last an acceptable period of time on unleaded fuel?". The answer to that is really "acceptable to who?". It depends on the view about engine life that the OE manufacturer took in the first place.
Aluminium - Any modern aluminium head (let's say post 1975) will have inserts that are able to run on unleaded petrol, even when the OE manufacturer says it is unsuitable. What they mean by "unsuitable" is that they are unwilling to guarantee the same 200,000 mile or so service life that they would expect from a post 1989 engine. They do not mean that the engine will suddenly and immediately fail just because you run it on unleaded petrol. In practice it will have no impact on the average car owner at all given that very few people keep their cars that long. If you have an aluminium head from a major manufacturer (Ford, VW, Peugeot, Vauxhall, Fiat, BMW, Mercedes etc) then stop worrying and just run it on unleaded. The worst that can happen is that eventually, in 100,000 miles or so, the valve seats will have pitted enough to need recutting but by then the chances are that the rest of the engine will be worn out too. There is no way the inserts will just burn out though in the same way as can happen to plain cast iron.
The full article is there in the link above. I have contacted MB UK and they are getting back to me with the answer.
