[cymbeline]

“be much more explosive”

An exploding mixture in the combustion chamber is what causes engine-harming ping. The mixture in normal operation burns over a small amount of time. There’s a flame front that sweeps across the combustion chamber.

Higher octane gasoline prevents detonation (pinging) at higher compression ratios. Higher compression ratios make engines more efficient which also means more horsepower per engine size.

A higher octane fuel contans no more energy than regular fuel.

The major limit to the efficiency of fuel-burning engines is the limted attainable compression ratio. It’s about thermodynamics. Diesels are more efficient than spark-ignited engines because of their higher compression ratio.

[IronJack]

But wouldn't introducing gaseous gasoline enable GREATER compression, since liquids don't compress but gases do?

I'll admit the pre-ignition problem is a big one, but not insurmountable, I don't think.

[painter]

The major limit to the efficiency of fuel-burning engines is the limted attainable compression ratio. It’s about thermodynamics. Diesels are more efficient than spark-ignited engines because of their higher compression ratio.

Bill and Ernie Elliot actually proved that in 1985 stock car racing in Nascar. This is before restrictor plates. Ernie, Bill's engine builder discovered a way to shape the combustion chamber to work at 13 to 1 compression. The result was more horsepower and better fuel mileage. Not only was Bill's T-bird faster than every one else's car he could stay out on the track longer. This was on the Super Speed Way tracks.