What are the differences in various grades of gasoline and how do they affect a vehicle?
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To understand this, we need to first understand how your average four-stroke gas engine works to generate power. There are four phases, four strokes, in the engine’s cycle:
1. Intake
2. Compression
3. Power
4. Exhaust
In the intake stroke, the cylinder draws fuel in. This fuel is then compressed in the compression stroke, then ignited by the spark plug in the power stroke; waste products are then vented in the exhaust stroke.
It’s the compression stroke that interests us here. The more you compress the gas/air mixture, the more power you can extract from it when you ignite it. However, the more you compress it, the more likely it is to ignite itself from the sheer heat before everything’s in position and the spark plug is ready to go.
This out-of-phase ignition not only means you’re not getting the right amount of power, but it can also seriously damage your engine — the “knocking” noise that it typically produces is the sound of bits of your engine smacking into one another.
Okay, so what’s that got to do with the octane rating, the number you see by the gas pump that dictates its grade? Well, the higher the octane rating, *the more resistant it is to premature ignition.*
This means that it will withstand being compressed more before it spontaneously ignites, meaning you won’t get knocking, meaning you’re not damaging your engine.
It should be noted that beyond that knock resistance, a higher grade of gasoline is not “better than” a lower one, and you’re just wasting money putting premium gasoline in a car that asks for regular.
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