Audi's A5 earns relatively good fuel-economy ratings--that is, until you venture into the heady performance territory of the S5 and the RS5.
The standard-issue, turbo four-cylinder A5 has a wide range of fuel economy ratings, starting with the best of the bunch, the front-drive Cabriolet with the continuously variable transmission and the all-wheel-drive Coupe with the six-speed manual. Both are rated at 26 miles per gallon combined, though the Cabriolet gets better city ratings and the Coupe fares better on the highway.
Step into the eight-speed automatics, and both the Coupe and Cabriolet earn identical ratings of 20/30 mpg, and 24 mpg combined.
The S5 sees economy suffer a bit, though its supercharged six is more efficient than the former naturally aspirated V-8. It's rated at 18/28 mpg with the Coupe and its dual-clutch transmission, or 21 mpg combined; with the manual shifter, the numbers are 17/26 mpg, and 20 combined. Cabriolets with the dual-clutch gearbox check in with EPA numebrs of 18/26 mpg and 21 mpg combined.
Bringing up the rear is the 450-horsepower RS5. Its V-8 and dual-clutch combo evades the gas-guzzler tax, but still registers the lowest gas mileage of the lineup at 16/23 mpg, or 18 mpg combined.
It's long been rumored that the A4 family of vehicles, which includes the A5, would adopt either Audi's diesel engines or the hybrid technology now found in its Q5 SUV. As of yet, neither's been confirmed for the A5 coupes and convertibles.