Octane required for 78-79 450????

[RickM]

I had a discussion with a pump jockey the other day after he was blown away that I was using 87 octane (regular) in my '85 380. I mentioned to him that the owner's manual recommended this octane. He stated that his wife's 78 (or was it 79) 450 required premium.

I'm thinking he was looking at the RON rating and not converting to the US octane requirement.

Thoughts?

[abe g]

Use 87 on my 1977 450sl manual calls for same! Your friends car obviously set on advance so possible knocks. tell him to adjust to fit 87 octane unless his high milage has built up carbon, other possibilities. Mine runs fine @ 130 thousand miles with 87!. Abe G

[RickM]

Thanks Abe. Does the manual specify 91 RON or 87 ron+mon/2?

[abe g]

stop knocking youself out! 87 octane is called for unless unusual conditions prevail for that engine. Abe G

[RickM]

Not knocking myself out...it's not even my car. I'm merely trying to determine what is published in the manual.