My wifes SL 320 1997 has a mpg gauge that is really a vac gauge but it reads the highest mpg at approx 50 mph. My 2002 Dwnali pickup has the instant and average mpg readings and same thing, 50 mph is best-17 mpg, 60mph shows 16 mpg and 70 mph shows 14mpg!

Dan

__________________
81 240D 4speed with 300D engine
87 560SL
2005 E320
Yukon Denali
Sierra Denali
850 Turbo Volvo
1996 Mustang
1984 Mustang race car
3 Boats