By Lauren Fix, The Car Coach
First, what is octane? 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 (like it should), it causes knocking in the engine. Knocking can damage an engine, so it’s not something you want to have happening. Lower-octane gas (like “regular” 87-octane gasoline) can handle the least amount of compression before igniting.So what octane do you use? 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. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.
So will a higher octane gasoline clean your engine better? As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car’s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.
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 the 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.
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 and friends with one preference over another. I personally have always followed what ever the manufacturer has stated 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, here’s the answer.
The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium’s anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can’t tell.
The Federal Trade Commission, in a consumer notice, emphasizes: “(I)n most cases, using a higher-octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner.”
But won’t the extra expense help my fuel economy? Actually, the price debate is nearly worthless. At 20 cents more for premium, pumping 20 gallons of premium instead of regular would cost $4 more. Annually, that’s a difference of $171 for a vehicle that averages 14 miles per gallon — as some vehicles do — and is driven 12,000 miles a year. So, if your fuel economy improved by 1 mpg, the saving could never be seen. The minimal increase in mpg is not made up by the cost. So you decide.
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 have adequate memory to allow for separate sets of instructions for various octanes and keep pushing to maximize performance on whatever grade of fuel is used.