Regular vs. Premium. Whatís the Difference?
Itís time to make that stop at the gas station to fill your vehicleís tank. You are all set, but before you can pump the gas, you have to choose what type: regular, mid or premium. What is the difference, besides the price?
Gas has an octane level. You have the regular gas, with an octane rating of 87; the midgrade at 89; and the premium at 91 or 92. So what does that mean? Basically, itís rating the percentage of octane and heptane. For example, 87 means the fuel has 87 percent octane and 13 percent heptane. The same applies to the midgrade, with 89 percent octane and 11 percent heptane, and premium, with 91 or 92 percent octane, and nine or eight percent, respectively, of heptane. This ratio tells you how much fuel can be compressed before it spontaneously ignites. So, the higher the octane, the more compression.
Contrary to popular belief, this octane levels donít mean they deliver more power. All grades of gas have basically the same amount of power, or heat energy. What this really means is that a higher octane level means it is less likely to cause your engine to make those knocking noises. When your engine knocks, it means the fuel and air mixture in one or more of your carís cylinders ignites spontaneously thanks to compression, and is separate from the combustion caused by the spark plug. This means youíre getting bursts of energy instead of a slow, steady burn.
So, which type of gas should you use? The answer is found in your ownerís manual. Today, most cars are designed to run on regular gas. However, if you have a high-performance car, most likely you will need to use midgrade or premium gas because the engine is designed for higher compression (read more power).
Sure, you can fill your tank with the midgrade or even the premium, but it doesnít improve gas mileage or make your car run any better.