There are currently only three models on the market that feature the 4.2 Audi engine. One of these Audi models is the A6 Sedan. Another Audi model featuring the 4.2 engine is the R8 Spyder. The Audi S5 Coupe is the third model currently equipped with the Audi 4.2 engine. This engine is relatively fuel economic, offering up to 23 highway miles per gallon. The 4.3 engine includes a two-stage intake system and direct injection. The Audi’s 4.2 engine has 350 hp and possesses the ability to accelerate from 0 to 60 miles per hour in only under 6 seconds.