No one knows. Not even Stihl-I asked them. I had an 056, which is now an 056 Super, and I was asking the same question. Depending on the model, 056, 056 Super, or 056 Mag II the consensus I got was starting somewhere around 5 hp, then to 6-ish for the Super, and something like 7+ for the MII. But where they really shine is in the torque department. The Super and the MII are still farvorite milling saws today. Very reliable and easy to work on. It's nice that they share many parts with the 045, as it makes parts more available, though they are still in demand.