Quote:
Originally Posted by tahdizzle
Driving habits and Octane are mutually exclusive.
If a car is "tuned for a higher octane" then its probably a requirement to use Premium octane.
If we take use that logic, a car tuned for "regular" Octane would get better MPG. Which is not true. Octane has an effect on Performance, but not MPG.
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Your driving habits typically do not change based on the output of your engine, for example person needs to reach 65 mph during the 200 feet it takes to merge onto the freeway. If an engine is running less efficiently i.e. one pulling timing due to a lower octane rating to prevent knock the engine will burn more fuel to reach the required speed over the allowed distance than an engine running more efficiently on the appropriate octane fuel that's capable of generating more power with the same amount of fuel.
Say it takes 50hp to maintain freeway speeds, in an engine that utilizes higher compression the combustion cycle is more efficient, a higher percentage of the energy in the fuel is converted to work. If all of a sudden you have to reduce that efficiency to prevent knock (again, pulling timing when using a lower octane) you have to increase the amount of fuel you are burning to compensate and maintain that speed.
Edit: I'm speaking very generally here, if you would like me to start pulling references and formulas I can.