Why do luxury car companies build engines that require premium gas?
In: Engineering
“Premium” gas is a way of saying gas with a higher octane. Octane is a measure of resistance to ignition upon compression of the fuel, and getting a higher octane requires additives which increase the cost of the fuel.
Being able to compress the fuel more without it exploding too early allows engines to get more power out of an engine without making it larger. This means if you want a higher performance car and don’t mind paying more for gasoline then you can design the engine to use high octane fuel.
A higher compression ratio in an engine allows for more power to be extracted from each stroke, which allows a more powerful engine in a smaller package. High compression ratios require higher octane fuel to prevent knocking.
One of the ways that high engines are made more powerful is by increasing the compression ratio of the air and fuel before the spark is fired. The octane rating of fuel indicates how much compression the fuel can withstand before it bursts in to flames on its own. This is called preignition, and it will damage the engine.
So in summary it needs higher octane fuel because the compression ratio is higher in order to make more power.
The design of the engine relies on higher compression ratios in the cylinders to deliver horsepower, and that requires higher-octane gasoline. ‘Premium’ gasoline has a higher percentage of octane in the fuel, with a smaller amount of the fuel being heptane than ‘ regular’ unleaded gasoline.
Earlier designs relied on large-displacement engines, with larger-volume cylinders, which typically used a larger volume of fuel to generate horsepower. Never engines have been designed differently, to use a smaller-displacement engine and get the same horsepower. That requires more power to be delivered from the fuel, which requires higher-octane gasoline.
Premium gas simply burns hotter and faster. It requires a different engine style to survive that extra amount of force, but when harnessed correctly the extra force translates into extra speed and acceleration.
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