Complete laymen so I’m going off some quick research. So I may be wrong on the issue.

How much energy is produced by the substance doesn’t matter if the substance can’t combust. I remember an old show used an example that in theory a Snicker’s bar has more energy than a stick of dynamite, but it’s composition isn’t prone to being explosive.

Pure gasoline thrown on a fire burns because it can pull the oxygen from the air itself. In an ideal situation the combustion chamber in your vehicle’s engine is sealed away from the atmosphere. So there needs to be another way to get the oxigen in there for the combustion chemical reaction to occur. Ergo, the oxidization additive.