What Happens If You Put 87 Octane in a 91 Octane Car?

What happens if you put 87 octane in a 91 octane car? Well, nothing much if you accidentally use it for one time or two. But if you keep doing the same thing repeatedly, you can expect to see some serious issues with your car.

In this article, we’ll discuss the effect of using 87 octane on a 91 octane car, along with the differences, how you can mix both of them, and whether the gas rating has to do anything with mileage or not.

So without any further ado, let’s get started!

What Happens If You Put 87 Octane in a 91 Octane Car?

Different engines are tuned differently, and they come with different fuel systems as well. Some engines have advanced technology fuel systems, and some do not.

And how using low-grade fuel will affect your engine depends on all those factors.

Usually, using low-grade oil occasionally does no harm, but you might experience low power and less mileage. And in some engines, using low-grade fuel can cause some serious damage.

For example, you will hear the engine knocking badly right after starting the vehicle. Or you might hear the valve chattering. These happen when the fuel isn’t burning right, and if you experience anything like that, make sure to get rid of the old fuel and fill it with the ideal one.

Having that said, there was a time when cars weren’t so technologically advanced, and when used low-grade fuel, the engine will start to knock immediately. But now, with the grace of technology, engines and fuel system can adapt to changes.

If you use low-grade fuel in a premium fuel technologically advanced car, its ECU system will help the engine adapt to it; the engine will adjust the timing and will perform accordingly without any trouble.

With that said, you shouldn’t use low-grade fuel continuously. Long-term use of low-grade fuel can take its toll on the engine.

So to end this, we can say that if your vehicle is technologically advanced and comes with a modern fuel system, you shouldn’t worry about the occasional use of low-grade fuel. But make sure not to do that regularly; that might hurt.

Is There Any Difference Between 87 and 91 Octane?

There are two types of octanes, premium and regular. 87, 89, these are considered regular octanes, whereas 91, and 93 are considered premium octanes. Some manufacturer recommends using premium octane in their vehicles, and some make it mandatory.

On the other hand, most of the vehicles run on regular octanes. Ever wondered what is there in premium octanes that make them premium? Let’s have a look at the major differences between premium and regular gas.

The only significant difference between these two octanes is the amount of the additive used. Apart from that, both octanes are the same unleaded gas suitable for every car. 91 octane contains a good amount of an additive that works toward making the gas more resistant to knocking or pinging. It is also called pre-detonation.

Gas can’t be compressed as long as needed and has a limit. The engine can compress gas heavily until it becomes hot and ignites without the help of a spark plug called pre-detonation. If that’s happening for an extended period, it can damage the entire engine.

On the other hand, 87 octane doesn’t come with much of the additive that makes the gas resistant to pre-detonation. So 87 octane can pre-denote faster than 91 octane. If your car engine is knocking or you hear valve chatter, that’s a sign that you should move to premium gasoline.

Another difference between these two is the power. 91 octane comes with a high amount of additive, which means they can be compressed to more than 87 octane. When they are compressed, they make more forceful explosions, resulting in more engine power.

Having that said, shifting to 91 octane doesn’t necessarily mean the engine torque or power will increase. It depends on some other factors such as how the engine is designed, how it adapts, etc.

87 or 91 Octane, Which Gas Is Best for You?

Whatever car you have, the user manual should tell you what kind of gas you should use. If that mentions, it is recommended to use premium gasoline (91, 93 octane) on the vehicle, which means it will be best for you to use premium gasoline, but the engine can work well with regular gas (87 octane) as well.

But when the manual says the engine requires premium gas, that’s the only way.

This Video Will Help You Too!

Frequently Asked Questions (FAQs)

What Happens If You Put 87 Gas In A Premium Car?

Using 87 gas on a premium car can cause extreme damage in the long run. But some premium cars can cope with regular gas as well. In that case, that shouldn’t be a problem. But it is still best to stick with what the manufacturer recommends.

What Happens If You Put 87 Octane In A 93 Octane Car?

You will hear the engine knocking or valve chattering badly if you put 87 octane in a 93 octane car.

Is It OK To Put Regular Gas In A Premium Car?

When a premium car has the ability to cope with both regular and premium gasoline, in that case, it shouldn’t be a problem. Otherwise, regular gasoline on an engine that requires premium gas would damage.

Can I Use 85 Octane Gas In My Car?

Yes, you can use 85 octane gas in your car if the engine is compatible with that.

Is 87 Octane Bad For Your Car?

No! As long as your car engine has the ability to adapt to that, it is not a problem.


If we summarize the entire thing, you can use regular gas on your vehicle if that can work well with that. Otherwise, you shouldn’t do that since that can hurt the engine very badly. Even though premium gas is heavy on the wallet, it saves your premium car.

Hope that helps you understand what happens if you put 87 octane in a 91 octane car.

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