Can anyone with a technical background out there explain why the Camry hybrid gasoline engine has a very high compression ratio (12.5:1) and still only needs regular grade gasoline? Normally engines with a high compression ratio require high octane (premium) grade fuel to avoid engine knock. Most engines these days do however I know have a knock detector to retard the ignition if a lower grade fuel is used to avoid engine knock damage. Retarding the ignition of course reduces the engine performance. This begs the question as to whether using premium fuel would increase the horsepower output of the engine. This of course would only happen if the engine ignition was advanced by the computer to take advantage of the premium fuel. I've also noticed that the apparently similar engine in the regular four-cylinder Camry has a lower compression ratio (9.8:1) and again wonder why.