Audi‘s Q7 SUV is getting a new Supercharged 3.o-liter (3.0T) engine for 2011, as well as an 8-speed automatic transmission, two features that will no doubt deliver vast improvements in fuel economy.

In a few cases, however, the latest automatic-transmission designs, including six-speed automatics, actually surpass their manual counterparts. For example, the Mazda3 i gets one more mpg with its ...