Which gasoline is best for your vehicle? Most of us believe that the higher the octane number (that yellow sticker on the gas pumps), the better performance and fuel economy we will receive in exchange for the higher price. So what’s the truth? Here’s the low-down on high-octane gas.

Octane ratings measure a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition. When gas ignites by compression and not by spark from the spark plug (as it should), it causes knocking in the engine. Knocking can damage an engine, so you want to avoid it. 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. Most people don’t know the compression ratio of their engine, so be sure to check what is the correct octane for your engine in your owner’s manual. Regular octane is recommended for most cars. Some cars with high compression engines, like sports cars and certain luxury cars, however, need mid-grade or premium gasoline to prevent knock.

Should you ever switch to a higher-octane gasoline? A few car engines may knock or ping, even if you use the recommended octane. If this happens, try switching to the next-highest octane grade. In many cases, switching to mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Today's engines are computerized and highly sensitive; they use a device called a knock sensor to adjust settings automatically for low-octane gas. The vehicle computers have engine controls that allow for separate sets of instructions for various octanes and keep pushing to maximize performance on whatever grade of fuel is used.

Is all "premium" or "regular" gasoline the same? The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while others may allow 90 octane to be called premium. To make sure you know what you’re buying, check the octane rating on the yellow sticker on the gas pump, instead of relying on the name "premium" or "regular."

What’s the bottom line? You’ll hear many stories from friends with one preference over another. I personally have always followed whatever the manufacturer states in my owner's manual to get the most performance I can. For those of you who are just looking to drive your vehicle and do the right thing, that’s the answer.