Standard vs Premium Fuels

[Ruan]

Does higher octance not also equal greater calorific content given higher octance fuels are longer chains of hydrocarbons?

Higher Octane essentially has nothing to do with H-C chain lengths.

"RON" is simply a measurement of how close to 100% Iso-Octane the fuels' Anti-Knock Resistance is... Petrol H-C chains are generally a set length - it's the additives that control it's Anti-Knock. It doesn't mean it contains Octane - lots of things can be added to fuel to increase its' RON number such as Toulene, MTBE and TEL (Tetraethyllead ala 4-star). Fuel with a pile of TEL in could reach up to 150RON!!

If you're interested in this at all, there's a whole load of different ways of measuring RON, MON and some places have the RM/2 method. 100% on the scale means it's 100% Iso-Octane, 0% n-heptane - a RON of 90 would mean 90% Iso-Octane and 10% n-heptane - it's simply a reference scale. You can however get substances that have a higher knock resistance than Iso-Octane - hence 102RON.

But yes, as said, you simply won't get any improvement in performance if your engine is up to it's mapped in limits - if you're not pulling any timing, then there's no more timing to add once it's not knocking!