Gasoline-related question

I don’t think Cecil has tackled this one yet: does premium or mid-grade gas do anything for the standard car? How about cars that say “premium fuel only?” Why does it cost so much more for premium gas? After all, isn’t it the cheap stuff boiled for another 30 minutes??

Premium gas just has more of the “good stuff” in it. If the cheap gas is “boiled” longer, it is to get the “good stuff” out. The refiner can then sell the “good stuff” and the cheap gas.

If the engine is designed for premium gas, you need to use it or make your own by adding octane booster to the cheap gas. Buying premium gas will be cheaper.

There was already a thread on this. Basically, higher octane is necessary for engines with high compression ratios. Due to physical laws governing the PVT of a gas (pressure-volume-temp relationships), high compression of a gas yields high temps which can induce auto-ignition of the air-fuel mix prior to when desired (that’s the spark plug’s job!) thus causing the tell-tale “engine knock”. Higher octane fuels permit greater compression of the air-fuel mixture by suppressing auto ignition. Thus, the risk of engine knock is reduced. Engine knock hinders an engine from performing at its best, engine wear-and-tear, etc.

(FYI: Compression ration is a ratio expressing how much the air-fuel mixture is compressed by the piston within the cylinder chamber. It compares the volume of the air-fuel mixture with the piston at its initial position to that of the volume of the air-fuel mixture with piston at its final position.)


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