Owners manual calls for "regular-grade gasoline min RON 92". Pretty sure that RON is European while we use (R+M)/2. Can't seem to remember the conversion. I've been running 89 octane (mid grade)and no pings. ANybody have the conversion? Any G-Wagen owners outthere?
Thanks J.R.

I have a 1981 280GE, I use the mid as well and it works fine. Power and no pings. As long as the engine is not pinging, you are fine with that octane.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I try to run 91 octane but have noticed no ping on 89. I don't know if your 280 is similar to my 300 but mine has a knob under the hood to retard timing if you can't find the higher octane.

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90 300GE 5sp
95 740iL

I have had no problem using regular. I also hardly can see the difference when I put the premo stuff in. In the end I switch back and forth just to keep things clean. My understanding is the stock 280GE low compresion is designed for lower grade fuel?

good point
 

The 460 chassis Gs had low compression pistons to allow the use of poor quality fuels all around the world. My '90 300GE had a knob underhood to retard timing in the event low quality fuel was all that was availible. The 280s unless fitted with high compression pistons should run on anything this side of Jack Daniels. Brent

Compression ratios
 

Yes. According to my owner's manual, the 280GE has an 8:1 compression ratio (the 230GE, however, has a 9:1 ratio). That's unnecessarily low in any vehicle used in this country (i.e., USA), and one reason why my newly rebuilt long-block (see my post elsewhere) will have special euro "car" pistons (giving a 9.25:1 ratio), for a major increase in horsepower (9:1 is normal in Euro cars -- this will be a tad higher). I'll probably need high octane fuel, but no matter -- I've always used high octane anyway, only for the increased additive package (detergent, etc.) that I've always felt was more generously added to high octane grades of gas.