It's a partial yes. You have to worry about pressure as well. You can burn fuel at a higher temperature by igniting the gas at a higher pressure. But there are

It's a partial yes. You have to worry about pressure as well. You can burn fuel at a higher temperature by igniting the gas at a higher pressure. But there are certain constraints due to the fuel. If the pressure is too high, the fuel will spontaneous combust. That's why there are different octane rating of fuels and why higher octane fuel gives you better fuel efficiency (given your engine has some sort of valve timing like VTEC). This is also why Diesel engines tend to have better mileage than gasoline engines. Even though gasoline engines will perform better at the same pressure as Diesel, there just no way to bring the gasoline to the same pressure that the Diesel can handle. When and how you combust the fuel can give you different fuel efficiencies as well. For instance, the Brayton cycle can achieve easily over 50% fuel efficiency. But in order to achieve this, you need a special housing (jet engines uses this cycle) to be able to compress the fuel to the specific pressure and also handle the pressure. Also, special fuel is required. These two things makes it not really practical for the standard consumer. On a tangent, Internal combustion engines is probably one of the funnest and hardest class I took in graduate school...