Unleaded Petrol - 1987 300SL

[Paul Woodman]

I am currently running my 1987 300SL on lead replacement petrol, but supplies seem to be getting harder to find. I have been told this model will run on lead free petrol without any problems - is this correct ?

If not, what needs to be done or where is the best place to obtain additives

 

[Arnie]

Unleaded Petrol

The main problem would be to check whether you have hardened valve seats in the engine. Probably you do. The other thing is then perhaps to adjust the ignition timing. Your MB dealer should be able to look up the data for your car and tell you what, if anything, is required.

In anycase, LRP was never really a good substitute for leaded.

 

[Andy]

Unleaded Petrol

Hi Paul

Don't worry about about using unleaded. Just use it. There is very little which can be done. Then ignition timing can only be adjusted slightly using the trimming plug. But uless you are travelling to a country with really low octane fuel. No alterations are required.

Regards

Andy @ www.mercedesservicing.com

 

[Arnie]

Unleaded Petrol

BTW...

Sh*ll
Optimax works really great. A little more expensive, but gives more power and slightly better mpg, which makes up for the cost difference.

It's nearly the same octane (97) as the old leaded (98) and so you shouldn't need any ignition adjustments.

The other (very) minor difference between leaded and unleaded is that the latter burns with a faster flamefront, hence newer engines tend to have shorter strokes compared to the cylinder bore diameter ("under-square").

Anyway, I think, as Andy said, you should not have any problems, especially as MB cars were also designed with the US market in mind, which went unleaded a long time before we did.

 

[Malcolm Brown]

Unleaded Petrol

I usually run mine on Optimax, but occasionally on unleaded.

I don't think your 87 will be any different from my 88 - but check the sticker inside the filler cap. If it says at the bottom, under the tyre pressure chart "SUPER (AUCH BLEIFREI)" it is definitely OK. Means "Super (also lead-free)".