What is an octane rating?
Octane is the rating of a gasoline’s stability or ability to prevent engine knock. Engine knock is not a noise that comes from the engine, but it is caused when air and fuel spontaneously detonate too early during the compression stroke in the engine’s cylinders. The air and fuel mixture should be ignited by the spark plug for proper timing, but engine heat and hot spots on spark plugs or cylinder walls during compression can cause it to ignite early. If your engine has uncontrolled knocking, also called pinging or pre-detonation, it can eventually cause severe internal damage.
What makes gasoline octanes different?
Have you ever pulled into a gas station to refill your vehicle and wonder why there are so many different types of fuel to choose? You may wonder why there are so many different fuel octane options, which ones are okay to put in your vehicle, or what makes them different. How do you decide which gasoline octane to put in your car? If you don’t know the octane requirement for your vehicle, you may be overpaying at the pump or putting the wrong type of gasoline in your vehicle. Read on to learn more about gasoline octane ratings and what they really mean.
What octane do I need for my car?
The octane level in the fuel your car needs depends on the manufacturer’s recommendation and engine. Most manufacturers use one of three classifications for the correct fuel: regular gasoline recommended, premium gasoline recommended, or premium gasoline required.
- If your manufacturer recommends regular gasoline, purchasing premium gasoline is likely a waste of money. Independent testing has shown no increase in fuel mileage or horsepower when using premium fuel in engines that are designed to run on regular gas. The engines in these vehicles will deliver optimum performance using regular gasoline.
- If your manufacturer recommends premium gasoline, you can use any fuel octane for your vehicle. However, you may see lower performance and fuel mileage from lower octane fuels. Mid-grade fuels, like 88 or 89 octane, may be a better and more cost-effective option, as they have shown to display similar performance when compared to higher octane fuels in these vehicles, but it is always best to follow the vehicle manufacturer’s recommendations.
- If your manufacturer specifies the use of premium gasoline in your vehicle, you should always fill up with the recommended octane. Using lower octane fuels will likely cause decreased engine performance and engine knock, which could eventually even result in premature engine wear or damage.
Does higher octane mean higher performance?
There is a common misconception that higher-octane fuels can increase the performance or horsepower from an engine. Higher-octane fuels actually release less energy during detonation than lower-octane fuels, which can mean diminished performance in engines that only need regular gasoline. The performance gain from higher octanes comes from how the engine is tuned. Engines with higher compression or cylinder pressure require less energy from gasoline to achieve optimum performance. This is the reason high-performance and luxury vehicle manufacturers often recommend fuel rated at 91 octane and higher.
What happens if I use the wrong octane?
If you use a higher octane than what is recommended, there is nothing to worry about. The good news if you only use one tank of lower octane fuel than what is recommended is that you will not notice any lasting issues. You will likely notice decreased performance or fuel mileage while running off of fuel with too low an octane rating, but if you use the correct fuel when you fill up the next time, these problems should disappear. However, if you continue to use too low of an octane fuel, you may inadvertently cause lasting performance issues and internal engine damage.
If you use a higher octane than what is recommended, there is nothing to worry about. The good news if you only use one tank of lower octane fuel than what is recommended is that you will not notice any lasting issues. You will likely notice decreased performance or fuel mileage while running off of fuel with too low an octane rating, but if you use the correct fuel when you fill up the next time, these problems should disappear. However, if you continue to use too low of an octane fuel, you may inadvertently cause lasting performance issues and internal engine damage.
What about Ethanol or Flex Fuels?
Most Ethanol or Flex Fuels are rated at 85 octane or “E85”. This octane should only be used in vehicles with Flex Fuel engines. Flex Fuel-ready vehicles usually have a badge on the side or back of the vehicle, and E85 will also be listed on a label inside of the fuel door. Most can run on E85 and all standard gasoline octanes. However, using E85 on a regular gasoline engine can cause severe damage to the engine or fuel system due to low octane rating.
We hope this helps you understand the difference in the variety of fuel octanes available at your local filling station, and that you now have a better idea which fuel option you should use in your vehicle. Using the correct fuel octane is essential to keep your car running at peak performance, so make sure to use the octane rating that is recommended by the manufacturer of your vehicle. You can also check out fuel system cleaners and fuel system additives for your specific fuel system needs so that you can keep your vehicle operating at its best.
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