Difference Between Regular And Premium Gas: Mixture Effect

What Happens When You Put Regular Gas In A Premium Car

Is it bad to mix regular and premium gas? Here are key things you must should know when you accidentally put regular gas in a premium car. Several issues can arise due to mixing premium and regular gas.

Scenarios likely to happen when you put regular gas into a premium car is that your engine efficiency can be reduced. In worst case scenario when you continue putting the wrong fuel in your car can result in knocking your engine. Besides, you are less likely to benefit from an insurance especially when the manufacture recommended not to use any other fuel except premium fuel.

Mixing Premium and Regular Gas

Generally, mixing a gas of lower octane level to a higher octane gas can be disastrous. It is because a high octane gas is much resistance to knocking than a lower octane gas. Regular gas has lower octane than premium gas.

However, accidentally adding a higher octane gas such as premium to a lower octane gas such as regular gas can have no much significant change in terms of damages. In fact, studies have shown improved performance when compatible high octane gas is added to low octane gas.

Accidentally mixing regular gas to premium once or twice is a while you are less likely to experience significant problems especially if you added a much less quantity of the wrong gas.

However, prolonged use of regular gas in a premium car is likely to negatively affect your overall engine performance. So, can you mix regular and premium gas? No. It can cause problems to your car. Nevertheless, you can accidentally mix the gases.

These Happens After Mixing Premium Gas And Regular Gas

1. Reduced Engine Efficiency

Normally, a premium car is designed to run efficiently on premium fuel. Besides, premium fuel has a much higher octane value compared to a regular fuel. Mixing the fuel makes it difficult for the engine to effectively burn the regular fuel to produce the needed energy.

Reduced efficiency can occur when you engine should use a higher octane fuel. Turbocharged engine require high octane fuel such as premium fuel to run efficiently. Using regular fuel will reduce the engine performance

Also, cars that are high performance with minimal tolerance may negatively be affected when a much lower octane gas is used than the recommended gas.

2. Difficulties In Starting Your Engine

Since the premium recommended engine is unable to effectively burn the regular gas to produce the much needed energy for starting, you are likely to have challenges to start your engine. In worst case scenarios, your engine can fail

3. Rattling Noise

You are likely to hear some funny noises from your engine that normally does not occur. As soon as you hear the unusual noise, do not ignore. Consult a technician.

4. Knocking Of The Engine

In the instance prolonged use of regular gas has occurred, the risk of the engine knocking is high. It is because regular gas has much lower octane levels than premium gas. The lower the octane level the less resistance to engine knocking.

Once an engine knocks, you will need a technician to check your engine in order to make repairs if possible. Sometimes the damage may have already destroyed the engine to a point of no return and you will have need an engine replacement.

5. Explosion

Mixing regular gas to premium will definitely alter the chemical properties of the gases. Since premium gas has a much higher octane level that regular gas, mixing of the gasses can result in heating up in the fuel tank. The rising temperatures can result in build up pressure and an explosion is inevitable.

6. Denied Insurance

Since your car is insured, you may want to get an insurance company to repair your car engine in the instance it fails. However, if it is proven that you accidentally put a wrong gas in your car yet the manufacturer manual clearly stated to put only premium gas the insurance company can back off.

You will have to pay out of your pocket for the damages caused after accidentally putting regular gas in premium car.

Do This After Mixing Regular Gas In Premium Gas Car

As soon as you realized you have accidentally put regular gas in a premium car, you have to act to save your car engine from further damages. Do the following

  • Safely park and switch off your vehicle
  • Call a technician to check on your engine or tow your car for repair
  • Your fuel tank, fuel lines, and fuel injectors will be drained
  • Engine repair if needed can be done
  • Severe engine damages will require you buy a replacement
  • If you will drain the fuel system yourself, practice safety
  • Do not drain the fuel by siphoning with your mouth
  • Ensure the area is free from flames
  • Always work in a well ventilated open space
  • Be sure to wear gloves
  • Clean any spills on your skin with water as soon as possible


Accidentally mixing regular gas to premium gas vehicle can damage your engine. However, accidentally mixing premium gas and regular gas can actually boost your vehicle performance.

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I accidentally put wrong gas in my car, what next? (The article covers putting the wrong gas in your car such as : E85, Diesel, regular gas, premium, 89, 91, etc)


What happens when you put regular gas in a premium car can result in reduced engine performance and in worst case knocking of the engine. Accidentally mixing wrong fuel in a car such as mixing regular gas and premium can be disastrous. Stop running your engine and have the fuel drained as soon as possible.

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