The Mercedes-Benz S550 4MATIC was a variant of the W221 S-Class that was introduced for the 2007 model year. The S 550 4MATIC was sold as the S500 4MATIC outside of North America. This variant was initially powered by Mercedes' M273 E55 engine. The M273 E55 was a 5.5L naturally aspirated V8 engine that generated 383hp. This engine was replaced in 2011 for the M278 engine, which was a 4.7L twin-turbo V8 engine that produced 429hp. The W221 S550 4MATIC was built until 2013, although the model series would continue in the next generation W222 Mercedes-Benz S-Class as the W222 S550 4MATIC.