I think that Mercedes used very hard valve seats anyway. You will be fine, if not, all that is done is a valve job with hardened seats. The only thing the lead does is lube the top end. As a tech in the Us, this is what I have heard for I have never seen leaded fuel with the exception of race and aviation fuel! My whole life has been with unleaded fuel and it is fine.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
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