Gas Octane Numbers and Why They Are Important

Gas Octane Numbers and Why They Are Important

As drivers, we all fuel up our vehicles multiple times each month without really taking into account what those octane numbers on the fuel pumps are describing. Some prefer the cost-effective route afforded them at pump ‘87’. Many are creatures of habit who have used the same octane for years without noticing anything detrimental happen to their vehicles. Others swear by the high octane ’93’ because they believe it is better to be safe than sorry. So, which number do you use? Moreover, have you ever asked yourself if they matter, why they’re essential, and whether you should care?

The Casey’s technicians who are providing automotive repair in Sterling, VA will be the first to say that you should care, which is why we are here to give you a breakdown with this helpful blog.

To gain a better understanding and help you provide your vehicle with the best automotive care in Sterling, VA, let’s take a trip into the internal combustion engine of the average vehicle.

Engine Cylinders, Pistons & the Crankshaft

Vehicles with combustion engines contain cylinders and moving pistons connected to crankshafts that, once ignited by the spark plug, are always turning. Through expanding combustion gases, the piston is pushed, which in turn rotates the crankshaft.  

A cylinder is a chamber where the gasoline is burned and turned into power; it is the central working part of an engine, and it is the space in which the piston travels. The number of cylinders in a vehicle vary, but most cars and SUV engines have four, six, or eight cylinders. If this sounds familiar, it is most likely because you have at one point or another heard someone say their vehicle has a four-cylinder, V6, or a V8 engine. Those multiple cylinders are commonly arranged side by side in a bank, or engine block.

Gasoline and Air

Inside the cylinders are where the mixture of gasoline and air burns. Now, when you have the correct octane fuel in your gas tank, the spark plug ignites the mix and the pressure from the resulting explosion pushes the piston down. However, if the fuel in your tank is not the optimal match to your engine, the heat can ignite the fuel before the spark plug fires. At that point, the early ignition can cause waves of pressure that rattle the piston creating a knocking sound. All of that can overheat the spark plugs, erode the chamber, and cause your vehicle to have poor health.

Octane Numbers

Taking into consideration all that you have learned up to this point, let’s get into it! Octane numbers tell you how resistant gasoline is to knocking. The gas at the pumps you frequent have been lab-tested by comparing the gas to two reference fuels. One is knock-resistant and, when numbered on the resistance scale, has a rating of 100. The other knocks easily, and its rating on the resistance scale is quite literally 0. These two fuels are combined to make reference fuels that the lab will use as a basis of comparison for the gas you are buying at the pump.

When fuel comes into the lab for testing, it is compared to those reference fuels. When a fuel acts just like the comparison mixture (reference fuel) with 87% knock-resistant fuel, it is labeled with an octane number of ‘87’. The same goes for 88-90 and 91-94. In other words, the higher the octane number, the more resistant it will be to knocking.

What Your Vehicle Requires

While knocking depends partly on the engine’s compression ratio, some engines need higher octanes to avoid as much. If you have been using a lower octane on your vehicle all this time and your engine doesn’t knock, there probably is no need to spend more money at the pump than you already do. However, being the best automotive repair shop in Sterling, VA, we will always recommend that you take a look at your owner’s manual where you should be able to find the specified octane for your vehicle’s engine. If it cannot be found your manual, give the manufacturer a quick call. Make sure to listen to your vehicle too; it is always better to be safe than sorry!

If you hear any engine knocking, our team has the professional training and experience to make sure your vehicle is in good hands and as good as new. No matter what you need, we will be able to provide maintenance services customized to you. Trust our shops in Sterling, VA and Chantilly, VA with all of your automotive needs, and make sure you take advantage of our automotive repair Winter Specials before it is too late! Contact us today at (703) 444-6900 to make an appointment.

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