I don't know about the new MB's but my 1986 MB really likes high octaine. Like 92. I tried to save a couple of bucks by using the lower priced stuff, but I really noticed a difference in the mileage I was getting. 86 octaine gets me roughly 18.75 MPG, while the 92 gets me around 23.5 MPG. Sometimes more. Especially if I slightly overinflate the tires a pound or two. The difference in price I think is well made up for with an extra 75 miles per tank! (Depending of course on how I drive and how late I'm running) Since I spend an hour and a half per day commuting almost exclusively on the freeway, I have time to notice these things. I'm going to try for 25 MPG with the tank I have now. I've heard people argue that the brand of Gasoline makes a difference. I haven't found that to be true. The only thing effected by different gasoline brands is my pocket book!
Kyle De Priest
1972 BMW R75/5 (Best there is)