Sadly the 350SL never had hardened valve seats so , as above , the best option is to have them fitted to enable the car to be safely tun on unleaded fuel .
I don't really agree with the comment above that it depends , among other factors , on ' how long the car is going to be kept ' as this approach just creates/stores up problems for the next owner of the vehicle ; please remember that , as owners of classic cars , we are custodians of little pieces of history that need to be preserved for future generations , otherwise the world will be a poorer place with no examples of our fine cars left to be appreciated .
For a definitive list of which cars have hardened valve seats , and which don't , I have scanned the following couple of pages from the Sept/Oct 1999 issue of the Mercedes-Benz Club Gazette , trusting that no one will mind me reproducing it here as it is yet another good example of the many merits of joining the 'official' club ; the information also resides in the 'technical library' area of the club website so is readily accessible to paid up members who don't have this issue of the Gazette .
There used to be a site
www.leadedpetrol.co.uk which listed all the petrol stations throughout the UK , of which there were surprisingly many ( one or two in most large cities ) still selling four star leaded petrol , as opposed to LRP . Unfortunately , the site seems now to have gone but I understand there is still leaded fuel available around the country .
The last option is to use an additive such as the one listed below , which claims to turn unleaded back into genuine leaded fuel
tetraboost
Further information on fuel matters here
FBHVC Fuel Information
