There’s a lot of confusion out there about labeling on some of Mercedes-Benz AMG vehicles. While the V8 engine is really a 6.2-liter (or a 6.208-liter, if you want to be completely accurate), many AMG vehicles are labeled “6.3”. Just 100cc doesn’t seem like much, but it can make a big difference under the hood. We’re here to offer two possible reasons the Mercedes-Benz 6.2-L engine is labeled 6.3.
Honoring Mercedes-Benz heritage
Mercedes-Benz is a long-running brand proud of its history of innovation. When Mercedes-AMG designed the new M156 6.3 V8 engine, they may have named it after the 300SEL 6.3, which was built from 1968 to 1972.
Just as the new M156 engine in AMG vehicles is the first engine independently designed by Mercedes-AMG rather than based on previous Mercedes-Benz engines, the Mercedes-Benz 300SEL 6.3 was revolutionary for its day. It placed an extremely powerful V8 engine in a vehicle that had previously only had 6-cylinders, creating a 2-ton sedan that had performance similar to the sports cars of the era.
Complying with German taxation regulations on motor vehicles
Where the United States has licensing fees for motor vehicles, Germany and other countries in Europe have an annual car tax which is determined at least partially by the size of the engine. In the early 1900s, this taxable horsepower was determined by a complicated formula involving the number of cylinders, their diameter and stroke length, and incomplete fractions were often rounded up. Later the measure for the tax became simpler, but some of the inconsistencies in measuring remained.
While there is no guarantee that the AMG 6.2-L engine labeled 6.3 has been the victim of these complicated tax rules, it may mean that Mercedes-Benz has rounded up on the engine size because of those German regulations related to taxable horsepower.
We haven’t specifically asked Mercedes-Benz about these reasons the 6.2-L engine is labeled 6.3, but they seem viable. You can always test drive a vehicle like the 2016 Mercedes-AMG GT to experience this innovation and history for yourself.