Why are there different grades of gasoline?

When you are running low on gas you need to pull into a gas station to fill up your tank. You may find it hard to choose the right type of gasoline for your vehicle. In this article, we aim to explain why there are different grades of gasoline. Here you can find out how long it takes to refuel a gasoline car.

There are different grades of gasoline for different vehicles. Manufacturers recommend which grade of gasoline is suitable for which vehicle, depending on different octane ratings. Octane ratings show how stable fuel is and a higher octane number means more stable fuel. Understanding the grades of gasoline will help you choose the right gas for your car.

It is common sense that regular gas is your cheapest option and premium the most expensive one. However, is premium gas a better option for your car? We’ll answer that and other frequently asked questions in this article.

Table of Contents

What is Gasoline made of?

Gasoline is a product of crude oil or petroleum, which is a fossil fuel. Unfinished gasoline from petroleum refineries requires blending with other liquids, such as ethanol. This is the process of making finished motor gasoline. This way gasoline becomes suitable fuel for spark-ignition engines.

When we talk about octane levels of gasoline, we talk about the isooctane to heptane ratio. For example, an 87 octane rating means 87 percent isooctane and 13 percent heptane.

What is an octane rating?

An octane rating that you see on different grades serves as a measure of fuel stability. What does that actually mean? Internal combustion engines fire at a very specific time. This shouldn’t happen too early.

If auto-ignition happens too early, it might lead to knocking and pinging sounds in the engine. Apart from being unpleasant, these sounds can cause damage to your engine.

Most modern cars use electric computerized ignition. They also use sensors to detect knocking and delay the initial spark. This can eliminate the knocking sound. Yet, it can still lead to the problem of the engine running less efficiently. The higher the octane rating, the lower the chances of the gas pre-igniting.

What are the different grades of gasoline?

These are the three main grades of gasoline, where the number refers to an average octane level:

  1. Regular gas – 87 octane – carries an 85 to 88 octane level rating.
  2. Mid-grade or plus gas – 89 octane, with an average of 88 to 90.
  3. Premium gas – 92 octane – carries an octane level rating from 91 to 94.

Some companies use other names for different grades of gasoline, such as super, super-premium, or ultra. Keep in mind that they all refer to the same octane rating, presented above.

Regular gas

This is the cheapest option that is the best choice for the majority of cars on the road. It is also better for the environment and poses less danger to your health. Regular gas will get you from point A to point B and it has a budget price. Since it has a lower level of octane, regular gas will burn faster and stronger when pressurized.

Mid-grade or plus gas

89 octane level offers higher performance than regular, 87 octane gas. It represents a slight upgrade on the regular gas. You can try switching from regular to plus gas in case of engine knocking or pinging. Mid-grade gas may help you get rid of those.

Premium gas

Luxury and performance vehicle manufacturers usually recommend premium gas. It is the best option for high-performance engines. Such engines have high compression ratios or turbochargers.

They need premium gas to run their best.  This type of gas costs from 30 to 60 cents more than regular. Premium gas also keeps your engine cleaner and it produces less pollution.

Is it better to get higher grade gas?

Most manufacturers optimize your car to run on regular gas. With that being said, if your car doesn’t require premium gas, don’t use it. That way you will save money and your car will still work just fine. Here are some extra tricks on how to save on gasoline costs.

Does premium gas clean your engine?

If you think that premium gas will improve your car’s performance, make it go faster, or run cleaner, you are wrong. The detergent additives in your gas optimize your car’s performance and help clean your engine.

Some brands go the extra mile to ensure a higher percentage of detergent additives than EPA requires. BMW, Honda, Toyota, Volkswagen, and Audi believe that a lower percentage of detergent additives lowers engine performance and increases emissions. Want to also learn how to get rust out of a gas tank? Check out our tips.

Does your car require premium gas?

You can find out if your car requires premium gas in the owner’s manual or inside the fuel door. If the answer is yes, fill up your tank with premium gas. In case your engine uses turbocharging, don’t skimp on premium gas.

When premium gas is unavailable, your car can run on regular gas once in a blue moon. Don’t make this a regular practice, though. Using regular gas when premium gas is required can cause damage to your engine. ECU (Electronic Control Unit) can adjust to a lower grade fuel at the expense of horsepower and fuel economy.

Can you mix different grades of gasoline?

Yes, it is possible to mix different grades of gasoline. You can read in more detail if you can mix regular and premium gas. Drivers sometimes mix these two types of grades. What they get is basically a mid-grade type of gas. This combined octane level is somewhere in the middle and the vehicle will survive this.

Despite the fact that it is possible, we don’t recommend that you do this. The premium gas won’t really benefit a car that is designed for regular gas. It won’t harm it either. On the other hand, if you’re using a premium car make sure you refuel it with premium gas.

Having said that, don’t panic if you unintentionally fill out your premium car’s tank with regular gas. However, keep in mind that your premium car needs the good stuff, the premium gas, to run smoothly. Using a lower grade gas for your premium can lead to engine knocking and reduced performance.

Wondering if you can mix old gas with new gas? We’ve got some answers ready for you.

A girl pumping gas at the gas station.

Choose the right gas for your car

Fill up your tank with the right kind of gasoline for your car. It’s that simple. Follow the car manufacturer’s recommendations. They outline how to properly care for your car. If you take proper care of your car, you will:

  • Reduce the risk of causing damage to your engine.
  • Save money by not wasting premium gas.
  • Keep your car in its most optimal state.
  • Avoid potential repairs.

Can you pump gas with the car running?

You can pump gas with the car running. Should you do that? No, you shouldn’t. The placards at the gas stations telling you to turn the engine off while pumping gas are there for a reason.

If you leave the engine on, you increase the chances of gas vapors igniting when they come in contact with static electricity. Static electricity can build up on your clothes and cause a spark when you touch the metal. This could be dangerous when mixed with gasoline vapors.

To avoid causing a fire at the gas pump, you can also take these safety precautions:

  • Stay off your phone as it can increase static electricity.
  • Don’t return to your vehicle while pumping gas, as this also increases static electricity.
  • Don’t smoke or vape while refueling.
  • Keep children and pets in the car to avoid them breathing toxic fumes and focus on refueling.
  • Don’t overfill your gas tank so you don’t end up spilling gasoline. You can find out here how long gasoline fumes are flammable after spill.
  • Use an approved portable container if you transport gas and remove it as soon as you reach your destination.

Pumping gas with the car running is illegal almost everywhere in the world and it is a serious public hazard. Make sure you turn the engine every single time while refueling.

Can you mix gas and diesel?

Under no circumstances is mixing gas and diesel advisable. If it happens by accident, at the gas station, don’t panic. Once you realize you’ve made a mistake, don’t start your car. If the fuel pump draws the wrong type of fuel into your engine, it can clog up your fuel system and cause irreparable damage to your engine.

Don’t leave the wrong type of fuel in your engine for a long time. Get an emergency tow to the mechanic. Trained technicians will know how to pump the wrong fuel out of your tank and rinse it with the right type of fuel.


Choosing the right type of gas for your car is not rocket science. We do hope that we’ve helped you understand the different grades of gasoline. Remember that there are no benefits to using premium gas if your car doesn’t require it. Take all the safety precautions we’ve discussed and just enjoy the ride.