gasoline pump with octane ratings

What is an Octane Rating?

Have you ever wondered what those numbers on the gasoline pump mean? You might see an 87, 89 or 91 on your gas handle, each with their own incremental price increase. These numbers are called an octane rating, which measures the ignition quality of your gasoline. The higher the number, the better the ignition quality — with one caveat. You have to have an engine that can take advantage of the higher rating. If your engine is not made to do this, you are simply wasting your hard earned cash.

Which Gasoline Octane Rating Should I Choose?

How do you know which gasoline octane rating to select? For this, you need to consult the owner’s manual. Read the section closely because wording will make all the difference. If your owner’s manual says something such as, “only gasoline with an octane of 89 should be used,” this means you definitely don’t want to go lower than an octane rating of 89, but going higher won’t make much difference to your car’s performance. If your owner’s manual says something to the effect of “gasoline with a minimum octane rating of 89 should be used in your gas tank,” this means you have the option of using 89 or higher.

What is Engine Knocking?

That may clear up what those numbers mean at the gas pump, but why is it important in the first place? Have you ever heard a knocking sound coming from your car? That knocking sound is likely combustion from gasoline igniting improperly within your gas tank. This happens most commonly when you use gas with too low of an octane rating. If you consistently use the wrong type of gas it will start to damage your engine. It’s not worth saving a few cents on the gallon to only end up with costly repairs down the road.

Engine Knocking Issues

Sometimes, engine knocking is a symptom that something is already wrong within your car. If you use high quality gasoline with the correct octane rating and still hear knocking, you will need to get a mechanic to run a diagnostic on your vehicle. The knocking may be a symptom of a malfunctioning spark plug, or perhaps your EGR (exhaust gas recirculation) system is not working correctly.

If you suspect you may have a larger issue lurking under the surface of your car’s hood, H.W. Automotive Inc can take a look and get to the bottom of the problem before it gets out of hand. Call to set up an auto diagnostic or tune up today.