Frank Enstein
Best. Day. EVER!
High octane gas has less heat energy(lower BTU content) in it because they use lighter solvents with higher ignition points and slower burn rates. Used to help build refineries, petroleum engineers everywhere that loved talking about stuff like that. The alcohol used in the blend has at best 75% of the BTU's that gasoline has but has an octane rating of about 106. Lower BTU's, less fuel mileage. Engines built to run only on E85 can have much higher compression to increase fuel mileage and power but still lose fuel mileage compared to similar gasoline only engines. What I am trying to say, if your engine is designed to run on 87 octane, there is no benefit from using higher octane without a different tune up. Just info.
Nope.
The chemical make up of pump gas changes literally weekly to try to match next week's weather. Race fuel is as close as can be made consistent from batch to batch allowing a finer tune-up than pump gas allows. Light aromatics burn very fast and can degrade octane rating. Light aromatics have much lower flashpoint temps and are much easier to ignite with a spark or heat/pressure. The "Winter" blends of fuel have a higher amount of the lighter, easier to ignite light aromatics. They don't have as much BTU/gal as heavier ones. That is part of why your fuel economy goes down in the winter. One reason why diesels get better fuel economy is diesel fuel is made up of heavier chemicals. Fuel economy drops off for diesels in the winter as well because they have to add lighter chemicals to raise the cetane rating (the opposite of octane rating so they will start when it's cold outside).