When arriving at the gas pump, the fuel type can be found on several different handles. Most of the pumps have unleaded and are rated at different octanes, but they are all different colors.
There is usually one handle for diesel fuel that is usually green. However, what happens if you put gas in a diesel engine because you mixed them up?
We will look into the differences between gasoline and diesel fuel to see if gasoline can be substituted for diesel fuel or vice versa.
We will also cover what happens if you do put gas into the diesel engine and what to do if this happens. By the end of the article, we will answer your top questions.
Differences Between Diesel and Gasoline
Diesel fuel has heavier molecules than gasoline. Because of density and viscosity, diesel fuel atomizes differently as well.
This means that dieel fuel has a higher flash point temperature and higher auto-ignition temperatures, and diesel fuel is naturally lubricating while gasoline is not.
With this in mind, gasoline is the opposite. Gasoline is lighter with smaller molecules. Gasoline has a lower flash point temperature than diesel fuel.
Gasoline automatically evaporates while diesel fuel does not, and gasoline has no lubricating properties. Gasoline acts more as a solvent.
Can You Put Gas into a Diesel Engine?
No, the diesel engine cannot run gasoline. Diesel engines lack spark plugs and use compression to ignite fuel. This means combustion will not ignite in the engine.
In addition to that, damage can happen due to gasoline circulating through a diesel fuel system. Diesel fuel requires lubrication that gasoline does not provide.
The whole gasoline will need to be purged and cleaned out of the fuel system before the vehicle can be started and driven.
What Happens if You Put Gas in a Diesel Engine?
Putting gas into a diesel engine will result in uncontrollable detonation, no lubrication, the engine stalling, and possible diesel pump failure.
Fuel injectors failure and engine destruction can occur leading to a large repair bill in a short amount of time. Let’s analyze these possibilities in a bit more detail.
#1. Uncontrollable Detonation.
The combustion and air-fuel mixture ignite differently in the gas and diesel engine. Gas will create incomplete combustion in the diesel tank stimulating large amounts of black smoke from the tailpipe.
The problem will also create detonation, which is an explosion of the fuel in the cylinder. This knock or ping noise tends to be noticed more during acceleration.
#2. No Lubrication.
Diesel fuel is needed to keep the components of the fuel system lubricated. In comparison, gasoline has little to no lubricating capability.
Without lubrication, the metal components will rub together and create friction. This will lead to an excess wear of the parts in the fuel system.
#3. Stalling Engine.
Since the combustion is happening at the wrong time and the air-fuel mixture is not being completed, the computer will be compensating and making small adjustments to the computer settings.
This can lead to a decrease in power and performance. Eventually the engine can stall. The sensors on the computer may also be contaminated or quit functioning properly.
#4. Failing Diesel Pump.
Contaminated gasoline may damage your fuel pump. Diesel fuel is an oil and gasoline is a solvent. Without proper lubrication, your pump will fail.
You really don’t want to damage this part. A new diesel fuel pump can cost between $1,500 and $2,500. Even you can complete all the repairs yourself, you’re still going to be spending your own money on the parts.
#5. Failing Fuel Injectors.
Fuel injectors will fail for the same reason the pump fails. Lack of proper lubrication will create excessive wear and not long after the injectors will also fail. New fuel injectors cost from $350 to $850 each.
#6. Severe Engine Damage.
Severe engine damage is going to occur, regardless of lubrication or flashpoint temperature. Just adding 1% gasoline to a full diesel tank can lower the flash point temperature by 64-degrees farenheight.
Flash point temperature will prematurly ignite and you are going to cause catastrophic damage. You may be looking at a new engine faster than you can clean the system.
What to Do if You Put Gas in a Diesel Engine?
If you mistakenly put gasoline in your diesel engine, take action. Here are a few steps you should take.
- Do not try to start it if you haven’t already. If you have started it, turn the engine off and park in a safe area.
- Call your tow truck and do not continue to drive your car.
- Better to let a mechanic deal with getting it running again. It is a great idea to use a diesel mechanic, but you also will need to have some time as it may take a while and it will cost a lot of money.
Even if we are professional mechanics, it is a job that takes a lot of skill, which is why it is hard for us to recommend doing it yourself.
To finish cleaning up everything in the car you are going to have to take off the fuel system and drop the tank to make sure the gasoline is out before using the vehicle again.
What About Diesel In A Gasoline Engine?
Let’s consider the reverse situation: using diesel fuel in a gasoline engine.
First, the gasoline will be diluted reducing the octane considerably. Octane is important to ignition.
If the octane is itself decreased, gasoline will ignite too early. Ignition occurs when the gas ignites, but the piston is still moving up, creating a pressure collision that causes knocking and cylinder damage to the piston and rod.
Gasoline has an octane rating of 87 through 93 and diesel only has a rating of 25 through 40. This means that if you put in just 2% diesel to your gas tank, you’ve already decreased your octane rating by a point.
If you were to put 10% diesel in, it would reduce it by 5 points, and that is more than enough at once, especially if you drove the vehicle putting additional stress on it.
Diesel fuel is heavy, and it will sink to the bottom of the gas tank. Since the mixture is going into the engine, it will cause deposits on the spark plugs, valves, and pistons.
If you drive the vehicle while it exhibits these problems it can and will cause serious internal damage to the engine.
If the cylinder were to fill with enough diesel fuel, it could hydro-lock and the cylinder head would simply explode cause a blown head gasket or cracked cylinder head, or it could be the last mile you drove it.
Despite the fact that diesel may be harmful, we have not yet covered the worst part. Any unburned diesel that does manage past combustion is gotten into the exhaust, and remains a serious vehicle fire risk because of the catalytic converter.
None of these are things to deal with, making the bottom line that at minimum, pay closer attention to what you are fueling with.
FAQs.
Q: Will gas ruin a diesel engine?
Yes, gas will cause detonation, a stalled engine, and damage to the fuel system and if you keep driving, permanent engine damage.
The only way to fix the issue is to clean out all gasoline from the diesel fuel system and engine before driving again.
Q: How much gasoline can a diesel engine tolerate?
Some manufacturers say that your diesel engine can tolerate up to 10% of gasoline in the fuel without being damaged.
However, even without visible engine damage, most of the components will wear out earlier than expected. The best advice is to avoid putting any gasoline in the diesel engine if you want to avoid unnecessary repair expenses.
Q: Will 1 gallon of gas damage a diesel engine?
If you just pumped a gallon of the wrong gas, it’s probably best to get the car towed rather than attempt to drive it.
Driving with that gallon of gas is possible and may not cause serious damage, but it’s a good idea to check with a professional before you do anything.
Q: Is diesel in a gas engine worse than gas in a diesel engine?
Gasoline in a diesel engine is typically worse. However, either option is not ideal since they are not designed to work, or, again, be used together.
With gasoline in diesel or diesel in gasoline, you could be looking at some serious mechanical failure that would take a good amount of cash to fix. Best to just keep what fuel type is in your vehicle the way it is supposed to be.
Q: Does gas float on diesel?
Diesel is denser than gasoline, so if you put both fuels into a container like a fuel tank, the diesel will sit on the bottom.
In a gas engine, this can be catastrophic if the engine pulls the diesel fuel from the bottom of the tank.
If you’ve put the wrong fuel in your vehicle, do not start it. Have it checked by a mechanic.
There are few things more serious than putting the wrong fuel in your vehicle, whether it is a diesel engine with gas or a gas engine with diesel.
For this reason, pay attention when you pump. Don’t become distracted and make sure to check what pump you are using. A few extra seconds at the pump can save you money later.
If you have put the wrong fuel in your gas or diesel engine, do not panic. The next thing you should do (after not starting it, of course) is have your vehicle checked over by a mechanic. If you haven’t started the vehicle, the fixes will likely be minimal, and not as expensive.