722.6 electronic 5 speed gets no better mileage than the 722.5 5 speed - e.g. EPA rating of 1997 S320 versus 1996 S320, both 17/24. 722.6 5 speed gets only slightly better mileage than a 722.3 4 speed and that on the highway only - e.g. 1996 S500 (15/21) versus 1995 S500 (15/20). The idea that more gears necessarily offers better fuel economy is widespread but seems to be overblown if not just sales BS. More gears allows the engine to operate near peak efficiency more often but results in more shifts which are inefficient. In manual transmissions it actually seems to be the other way around - fewer gears offers better fuel economy. Corvettes sticks skip gears to avoid gas guzzler tax. Saab put out a bulletin in a prior fuel crissis telling their customers to skip gears (1 - 3 - 5) for better gas mileage. I've noticed over the years that 6 speed sticks will ususally have lower EPA ratings than the same car / drivetrain with a 5 speed stick. But still the myth persists that 6 speed sticks offer better fuel economy. The other great myth is that 6th gear of a 6 speed is necessarily taller than 5th gear of a 5 speed, as if they are taking the same transmission and tacking on extra gear.