WHAT THOSE NUMBERS AT THE PUMP REALLY MEAN.
You pull up to the pump and you see
the numbers, but what do they mean? Sure, your manufacturer told you which one
to use, but you’re still curious as to what’s the difference between 87 and 92
octane. Hopefully, this will help.
Let’s start off with a brief
discussion of how gas works in your car. Most cars use four-stroke engines. The
compression stroke is where the
engine compresses a cylinder-full of air and gas into a much smaller volume
before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A
typical engine compression ratio is 8-to-1.
The gasoline octane rating tells you how much the fuel can be compressed before
it spontaneously ignites. When gas ignites by compression rather than because
of the spark from the spark plug, it causes knocking in the engine, which causes damage. Lower-octane gas (like
"regular" 87-octane gasoline) can handle the least amount of
compression before igniting.
The compression ratio of your engine determines the octane
rating of the gas you must use in the car. In order to increase the horsepower of
an engine, increase its compression ratio. In other words, the higher
compression ratio the higher-octane fuel that is required. This is why they
call the “high performance” engines. While higher compression rates mean higher
performance and probably a little more fun behind the wheel, the disadvantage
is that the gasoline for your engine costs more.
So unless your vehicle manufacturer requests a higher grade
of fuel, you probably don’t need it and can save yourself a little money. Then
there’s always the matter of preference. If you feel that your vehicle runs
better with a higher grade of fuel, then by all means do what feels right to
you. Just be sure to check with your vehicle manufacturer.
