Is Unleaded Gas the Same as Regular?

Unsure if you're putting the right gasoline in your car? Find out if unleaded gas is the same as regular gasoline and what this means for your car.

Is Unleaded Gas The Same As Regular

When you hit the gas pump, you see plenty of options available to you. If you aren’t sure what’s best, it can cause a lot of confusion. For example, is unleaded gas the same as regular, and what is premium gas?

In this article, we talk about unleaded gas and regular gas, giving definitions for both. We also examine the differences between regular fuel and other options at the pump. At the end of the guide, we outline how to choose the right fuel for your vehicle.

Is Unleaded Gas the Same as Regular?

Yes, unleaded gas is the same as regular since leaded fuel was outlawed in the 1970s due to neurological issues.

However, there are various octane levels of unleaded gas, making some varieties considered a premium option instead. That’s why it’s important to know the differences.

What is Unleaded Gas?

Unleaded gas contains no lead. This formulation was released in the 1970s as an alternative to the previously-offered leaded gasoline. Unleaded fuel is better for the environment and health of motorists than leaded gasoline is. However, it’s also more expensive to manufacture. 

Originally, lead was used because it increased the octane level of the fuel. With this higher octane level, there were fewer instances of pinging or knocking as combustion occurred. Yet, it could no longer be used because neurological issues were cropping up in people, especially children, as a result of the fuel. It was also increasing the amount of pollution in the air. 

There are some older models on the road that still require leaded fuel. You can also find it used in some race cars for added performance. However, it’s been almost entirely replaced in the United States 

What is Regular Gas?

Regular gas is a form of unleaded gasoline. It contains a lower octane level than those labeled as premium gas. It’s the most commonly used in today’s vehicles and is labeled with an “87” octane rating.

Regular gas can be used in most cars today unless it’s a high-performance model or a luxury vehicle. It’s also the most inexpensive option as far as unleaded gasoline is concerned. 

RELATED: Can You Use Regular Gas in a Flex Fuel Vehicle?

Regular vs. Premium Gas

1. Octane

The octane rating between regular and premium gas is different. Octane refers to the fuel’s ability to withstand a certain level of combustion. In the combustion engine, air and fuel are compressed to be ignited through an explosion. This mixture must be ignited at just the right time to ensure pre-ignition doesn’t occur. If it does, the engine will make a knocking sound. It will also cause performance issues and can lead to engine damage.

Regular gas octane is rated at 87. Premium gas goes higher than this, often 89-94. The higher the octane is, the more it can withstand pre-ignition for better engine protection. 

2. Price

Gas isn’t cheap anymore these days, no matter what you do. However, regular unleaded is going to cost far less than premium fuel types.

On average, you might spend twenty percent more to put premium fuel in your vehicle. When that is what’s required by the engine, the small difference is better than damaging the car engine, but it does add up. 

3. Engine Compatibility

The majority of cars on the road today rely on regular unleaded gas. It’s the perfect addition to most cars, trucks and SUVs for optimal engine performance.

On the other hand, it’s recommended for some vehicles to use premium fuel. If you drive a luxury model or high-performance vehicle, you might see that premium fuel is recommended. If you are in doubt, read the owner’s manual or ask your local dealership what is best. 

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Regular vs. E85 Gas

You might have noticed E85 gas is recommended for some newer models. What is E85 gas and how does it compare to regular? You also want to know if these fuels are interchangeable.

To start, ethanol is a renewable fuel source that’s manufactured from plant materials, otherwise referred to as biomass. Regular unleaded fuel does contain some level of ethanol in the formulation. In most cases, the fuel is considered E10, which means it is comprised of ten percent ethanol to ninety percent gasoline. This formulation provides the right amount of oxygen to the fuel.

Newer cars can be termed as E85 flex fuel. This means that regular unleaded could be used or you could choose E85 fuel. This blend is established as 85% ethanol and 15% gasoline. Ethanol burns faster and creates less pollution, but it doesn’t produce as much energy. Plus, it’s not always easy to find unless you live in the Midwest region, where it’s usually created. 

RELATED: Ethanol (E85) vs Gasoline – Differences (Pros & Cons)

Why is Octane Rating Important?

The octane rating of fuel is one of the most important factors. This number determines how compression occurs of the fuel in the engine. The higher the octane number is, the more compression can occur before it detonates. 

Detonation is required at a particular interval to ensure protection from engine damage. That’s why motors are all rated to be used with a particular octane fuel. If your vehicle is supposed to be driven with premium fuel, it might still run on one with a lower octane, but the performance isn’t going to be the same, fuel economy may suffer and you could cause engine damage down the road.

How to Determine Fuel Octane

1. Car Manual

The best place to find the appropriate octane rating is in the car manual. Inside the owner’s manual, you will see precisely what the manufacturer recommends. If you don’t have the car manual, you can look at a copy online.

Remember that this recommendation doesn’t automatically mean that’s all you can use. However, if the octane is specifically dictated as the only option, you should follow that recommendation because the automaker knows best. 

2. Talk to Dealership

If you can’t seem to find a car manual, you could reach out to your local dealership or automaker through a contact form. It’s possible to get more information through one of these avenues.

Dealership technicians can look up the information specifically related to your vehicle. It’s best to get their advice, especially if you are looking to get warranty repair from them should anything go wrong. 

3. Test Options

If the owner’s manual doesn’t require that you use one particular type of fuel, you can do some experimentation. Try the car out with multiple octane ratings to see what suits you better. Ideally, you will run the tank down as low as possible before trying another fuel, just to be sure you get a clearer picture of the differences.

Additionally, you may find a time when changing the octane makes sense. For example, if you are towing heavy loads or putting the engine under unusual amounts of stress, it might pay off to upgrade to premium fuel temporarily. Use your best judgment while always following the recommendations of the automaker.

Does a Vehicle Go Faster By Changing to Premium Gas?

The car isn’t going to gain any more speed simply by adding premium gas to the tank. The octane rating is related to how the fuel compresses. If the octane rating is increased, it simply allows it to be compressed more before detonating. Since detonation can lead to engine damage, it’s important that you follow the octane rating that’s recommended by the manufacturer.

What you might find by upgrading to a premium fuel is that the engine runs smoother and more efficiently. It can also provide more protection against damage. The opposite is true if you decide to downgrade to a lower octane level. The engine can’t run as efficiently, so you might go through more fuel in the long run. 

Can Premium Gas Damage My Car Engine?

You could create engine damage if you use the wrong fuel in your vehicle. For example, if you were to put diesel fuel in a gas engine or vice versa, you can expect a lot of problems. The same isn’t necessarily true by using the wrong octane. 

However, car engines are designed to run on a particular fuel octane. You might think you are doing good by upgrading to premium fuel, but that’s not necessarily the case. You could create more damage than good. 

On the other hand, it could be more devastating to run a lower octane fuel in a car that requires premium. Your engine needs this extra protection to run properly if that’s what the automaker recommends. You shouldn’t deviate from these guidelines unless you want decreased performance and possible engine failure in the future.

Gasoline FAQs

Is it OK to mix gas types?

Yes, it is fine to mix different types of gasoline in your car. However, if you combine two different types of gasoline, it will result in an octane level in the middle of these. If your car is made to run on premium fuel, and you mix it with regular, you can notice some issues, though.

What happens if I accidentally put the wrong gas in my car?

If you put unleaded gasoline in a car that requires premium fuel, the car can run poorly in the worst case if you drive carefully. You may notice a loss of power and acceleration, as well as increased fuel consumption. However, if you accidentally put gasoline in a diesel car, you shouldn’t start the engine at all as it can lead to severe damage.

What happens if you accidentally put unleaded in a premium car?

If you accidentally put unleaded in a car that requires premium fuel, you may notice that the car doesn’t perform as well as it usually does. The engine may run a little rough, and you may notice decreased power and torque. If you do this by mistake, drive your car carefully until you refill the car with premium fuel.

Is 87 octane the same as unleaded?

Yes, 87 octane is the same as regular unleaded gas. Octane above 91 is usually considered premium gasoline. The octane rating of a fuel is a measure of its ability to resist “knocking” or “pinging” during combustion.

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Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.