Regular, Mid-grade, and Premium Gasoline: Know the Differences

by Stephanie Wallcraft

You’ve just bought a new vehicle, and you’re about to fill up the fuel tank for the first time. But how do you know what kind of gasoline it needs to run at its best? Is more expensive gas worth the extra money, and does your car even need it?

In Canada, the typical fuel station will have three to four types of gasoline available: regular, mid-grade, and premium are standard, and many stations will offer an ultra-premium grade as well. Here, we’ll take the mystery out of the differences between these grades and explain how to determine which one is the right fit for your vehicle.

Gas pumps regular extra supreme

What Does Octane Mean?

Octane is one of the flammable hydrocarbons that is naturally present in gasoline. The octane rating found on the different grades of gasoline is related to the refining process: fuels with a higher octane content are more expensive to refine and cost more to store and distribute due to lower demand. Those added costs are passed on to you at the pumps when you choose a higher-octane fuel.

Here’s why octane matters. An internal combustion engine creates power by filling each of its cylinders with a mixture of vaporized fuel and air, then lifting the piston upward into the cylinder to compress that mixture. The spark plug then creates a spark that ignites the fuel, and the resulting explosion pushes the piston back down the cylinder so that it can refill with the air and fuel mixture and the cycle can begin again.

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To get more power from an engine, the amount that the fuel mixture is compressed within the cylinder is increased. When everything is working as it should, the fuel mixture ignites fully and evenly. When it isn’t, the mixture may ignite on its own prematurely while being compressed, which creates what’s called knocking, a pinging or knocking sound the engine produces when this problem is occurring. Over time, persistent engine knock can damage an engine and hamper a vehicle’s performance.

Sometimes, the fuel mixture may spontaneously combust on its own before the spark plug fires, a process called pre-ignition. Engines designed for better performance are more prone to premature ignition because of their higher compression ratios. Higher-octane fuel burns more slowly when compressed and ignited than lower-octane fuel, which makes it more resistant to pre-ignition and knocking and therefore better suited to higher-powered applications.

Modern engines include knock sensors, which detect knocking and adjust the engine’s timing. This can mitigate the damage caused by pre-ignition, but a driver may find that the car’s acceleration becomes lethargic in response. Increasing the octane rating of the fuel used in the vehicle will prevent the knock sensors from engaging and improve performance.

Gas pump filling car

What are the Different Types of Gasoline?

Regular Gasoline (87 octane)

Regular gasoline in Canada is typically rated at 87 octane. This is the least expensive type of fuel and is also the grade recommended for use in most engines that don’t specify a need for a higher octane rating.

Mid-Grade Gasoline (89 octane)

Mid-grade gasoline is typically rated at 89 octane in Canada. A few vehicles call for it specifically, but it’s also useful in specific scenarios. For example, some engines that call for 87 octane will knock when regular-grade gasoline is used in high-demand applications such as towing, and filling up with mid-grade temporarily will resolve the knocking in those instances. Some engines will also begin to knock while using regular fuel as they age and may benefit from a switch to mid-grade over time. For the most part, however, there’s little benefit to filling up with mid-grade gasoline or higher if your engine doesn’t need it, and it’s not a suitable substitute for premium gasoline if that’s what your engine requires.

Premium Gasoline (91 octane and above)

For the most part, the gasoline labeled as premium grade in Canada is rated at 91 octane, though several brands also sell an ultra-premium 93 octane or 94 octane fuel at select stations.

These grades are the top tier and most expensive types of fuel with the ultra-premium grades coming at the highest cost. If your engine calls for premium fuel, you’ll need to use it consistently to prevent the long-term damage caused by knocking. In fact, filling up with a lower-octane fuel may even void your vehicle’s warranty if it causes engine damage.

Some car manufacturers will say that, for certain engines, premium fuel is ‘recommended.’ This means that the engine will operate at its best and produce more horsepower with premium gas, but the vehicle can also be fueled with 87 octane fuel without causing damage to the engine. However, the engine’s power output will be lower with regular fuel than it will be with premium fuel. When premium is recommended but not required, it is possible to switch between high-octane and regular gas – whether due to price, availability, or a short-term need for slightly better performance – as often as required with no risk of adverse outcome for the engine.

Petro Canada gas station

How Do I Know Which Grade of Gasoline to Use?

The vast majority of cars that require or recommend premium fuel will say so on a sticker inside the fuel door or on the gas cap. However, this is not a universal rule, and used vehicles may have had these stickers removed. The safest bet is to check the owner’s manual for the automaker's recommendation, where the octane level required by the engine will always be specified.

In summary: if your car’s engine requires premium fuel, you’ll need to use it. Lower-octane fuel could damage the engine, or at the very least cause it not to perform at its best, and you risk voiding the vehicle’s warranty if you don’t fill up with the grade it requires.

If your owner’s manual specifies that your vehicle’s engine needs mid-grade fuel, you should use it. If your engine takes regular fuel but you’re noticing knocking due to the engine’s age or driving in a high-load situation, try upgrading to mid-grade fuel to see if it helps.

If your car calls for regular grade fuel, it’s best to use regular when filling up at your favourite gas station. Apart from the scenarios outlined above, there’s no great benefit to paying more for a higher-octane fuel when your engine doesn’t require it.

All grades of gasoline are required by Canadian law to have a minimum level of detergents and additives, which act to keep your engine clean and free of deposits. Therefore, buying premium fuel when your car doesn’t need is unlikely to be the best use of your money.

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