What Happens if You Put the Wrong Fuel in Your Car?

Ever wondered what happens if you use the wrong gas in your car?

While you may be saying, “I’d never do that!” – this is something that does happen on a pretty regular basis to many drivers, whether it is a case of not knowing what the right fuel is or just a slip of the mind.

So what does happen when you put the wrong gas in your tank? Here are some of the possible things that can go wrong, as well as what you should do in the event that this happens to you.


Diesel Engines vs. Gas Engines

An engine that requires diesel fuel combusts fuel differently than a car’s engines that requires gasoline. Typically, gas stations have different types of nozzles for gasoline and diesel fuel. They look different and have different shaped nozzles that should not fit into the incorrect type of fuel tank. This makes diesel and gasoline more difficult to mix up, but, mistakes do happen.
Mid Section Of Person Refueling Car's Tank

Diesel Fuel in a Gasoline Engine

What Happens if You Put Diesel Fuel in a Gas Engine?

Theoretically, diesel fuel should not ignite in an engine that requires gasoline. This is because diesel fuel does not vaporize the same way that gasoline does. Gasoline engines are not designed to burn this type of fuel. Once your tank runs out of any gasoline, your engine will shut off as it can not burn the diesel fuel.

What To Do If You Put Diesel Into Your Gas Engine

If you do put gasoline into your diesel engine, or diesel fuel into your gas engine, the best thing to do is to turn off your engine as soon as you realize the mistake. This will help prevent damage to your internal engine components. Then you will need to drain out your gas tank and fuel lines. While you might be able to do this yourself, it is safest to ask for professional help with draining your cars fuel lines.

Gasoline in a Diesel Engine

What Happens if You Put Gasoline in a Diesel Engine?

A diesel engine can sustain damage immediately after having gasoline put into it. Gasoline is more combustible, meaning it will detonate faster, causing misfires, reduced engine power, knocking, and potentially cause permanent damage to your engine.

In newer “clean diesel” cars, any amount of gasoline in the system will damage the very sensitive emissions controls. However, burning straight gasoline in any diesel engine will almost certainly cause irreparable damage.

What to Do If You Put Gasoline Into Your Diesel Engine

Once you have realized the wrong fuel has gone into your diesel engine, turn your car off right away. Never force drive your diesel engine with gasoline fuel, if possible have your car towed, as the potential damage from driving your car will almost certainly be more costly. You will need to see a qualified mechanic to have both your fuel lines and the gas tank drained completely. Improper draining can cause further damage to your engine. If you think you have put gasoline into your diesel engine, schedule an appointment with your local AAMCO Colorado location right away to meet with one of our expert mechanics.


Let’s Talk Octane

Octane Ratings

Young businessman in a suit refueling car tank at fuel station
Regular, mid-level and premium are the three tiers of gasoline available at most gas stations. Each grade comes with a different number that refers to the octane rating of the gas. The octane rating is a measurement of the fuels ability to resist knocking or pinging as the fuel is combusted in your car’s engine. Typically, the higher the octane rating, the higher the price.  Related: Which Gas Should I Use?


Using the Wrong Octane

Putting the wrong octane fuel into your car is a very common mistake. The fuel nozzles are all the same design and next to each other at the fuel pump. In addition to this, it can be tricky to know what the differences are between octane levels.

What Happens If You Put In Higher Octane Fuel Into An Engine That Doesn’t Need It?

There is a pervasive myth that using a higher-octane fuel is better for your car’s performance. Hint – it’s not. Typically, although there are some variations among engines, putting a higher-octane gas into your car than it requires will neither help nor hurt your car’s performance. There are some engines that are not designed to burn higher-octane fuel and you may see a reduction in power and fuel economy.

This mistake should not cause any major damage to your car – just be sure to pick the correct octane gasoline next time you fill up.

What Happens If You Put Lower Octane Fuel Into An Engine That Requires High-Octane Fuel?

Whether done by mistake or done to try to save on fuel costs – putting low octane fuel into an engine that requires a higher octane can cause problems that destroy your engine.

If you fill an engine designed to run on high-octane gas with a lower octane than recommended you will notice effects almost immediately. You will notice a poor engine performance. Depending on how long you have been using the lower octane fuel the erratic combustion produced from this error can cause over-heating and irreversible damage to your engine.

If you have filled your engine with a lower octane fuel than it requires then you should switch back to premium high-octane fuel as soon as possible. If you have been using lower octane fuel for an extended period of time it is best to get some diagnostics run by your mechanic to check for any lasting damage.

Related: What’s Wrong With My Fuel Pump?


Total Car Care with AAMCO Colorado

Making sure your car is filled with the correct fuel for your engine is an important part of car maintenance. AAMCO Colorado is here for you – our total car care specialists can help with all of your car maintenance needs.

AAMCO Colorado has locations throughout the Colorado Front Range. Schedule an appointment with your local AAMCO Colorado location today and keep your car running smoothly.


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