Let's just keep some perspective with numbers like this; peak power and peak efficiency are different for different apps, engines, and situations. For example, NASCAR engines run in the 220-240 range on purpose. It has a lot to do with not getting the intake charge too hot (which makes it expand and less dense), and and the combustion process itself (which VERY generally gets more efficient with higher temps). So a set temp as 'best' for everything is not realyl the case.