It has been an average of 25-30˘ between grades here for the past couple of years or so. Means 50-60˘/gallon between 87 and 93 octane. I run premium in the Honda since it returns an easy 5-6mpg better fuel economy (~100 miles per tank), despite the car being designed for "regular" 87 octane fuel. The cost is a wash between the two, but the car runs better and I can go longer between fillups with the high-test.

The SL gets 93 octane on principle. It will run on 87, but once it gets hot, it starts pinging which doesn't do it any good.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]