How is gasoline different from diesel, and why does it damage the car if you put the wrong kind in the tank?
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Diesel requires a lot more heat to ignite. If you pour it on the ground and hold a lighter to it, it won’t burn. It’s also a lubricant that keeps the moving parts in a diesel fuel system lubricated and working smoothly.
Gasoline is a lot more volatile. It evaporates quickly and the vapors it emits are extremely flammable. That’s why people use it to start fires. It’s also a solvent, meaning it dissolves other substances and cannot be used as a lubricant.
Putting diesel in a gas car will just shut it down as a gas car cannot burn it. The fuel system now has a lubricant in it and all that has to removed before it can run again. Diesel nozzles are actually larger to prevent doing this, most people won’t try to fill their car with a nozzle that won’t actually fit in their car.
If you put gas in a diesel vehicle, it will run and you may not notice a difference initially. Since gas is more volatile, it will over heat your exhaust and melt different parts of it. It’s like putting a flame thrower down the exhaust. Gas being a solvent means that those fuel pumps that need diesels lubricant properties is no longer there. The low pressure and high pressure pumps will begin to break down. The metal lines in the high pressure side can begin to rust and all that debris can block things further down the line.
Spark ignition and diesel engines achieve combustion differently. Spark ignition ignites the fuel-air mixture with a spark plug, whereas diesel engines ignite fuel by compressing the fuel until it ignites on it’s own.
This leads to different requirements from the fuel. Spark ignition engine fuel has to survive compression and ignite only when the spark plug fires, whereas heavy fuels for diesel engines have to ignite under compression.
Gasoline and diesel are optimized for each of these two engine cycle types. This is also what the octane rating gasoline fuel is dealing with; there’s an additive that slightly changes the resistance to compression, and so gasoline with a higher octane rating can be used in engines with slightly more compression prior to the spark plug firing, which ends up being a higher performance engine. Also, contrary to popular belief, higher octane rating gasoline does **not** mean it’s a “better” fuel. It only means its rated for use in higher performance engines.
Anyway, using the wrong fuel in the engine can lead to issues. Gasoline in a diesel engine will detonate really really early, causing damage to the internals of the engine. Diesel in a gasoline engine can actually function, but most of the fuel won’t burn. You can end up with a serious amount of gunky partially-combusted diesel coating the internals of the engine, which can interfere with the oil on the cylinder walls or end up in the crankcase, which will cause damage over time if not cleaned up pretty quickly.
Of note though; each of those fuels *can* be used in the other kind of engine with modifications and proper control and calibration, but it’s somewhat difficult and not something the layman would be able to do on their own.
You got some good explanations on the mechanical side, so I’ll chime in on the chemistry side. Gasoline and diesel are made up mostly of hydrocarbon chains. Carbon forms four bonds and hydrogen forms one, so these form the basis for an enormous amount of chemicals. Methane is the simplest hydrocarbon, which is a carbon with four hydrogens attached. If you pop a hydrogen off of one side of two methane molecules and attach them to each other, you have an ethane molecule. Pop a hydrogen off one end of either side, and you can continue adding links to the chain for a good long while; methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, etc.
Shorter alkanes (what the simple carbon-carbon chain structures are called) are obviously much lighter and more volatile, and increasing the chain length makes them heavier and less volatile: The first few are gases, becoming increasingly easier to condense into a liquid as they get heavier. The next few become liquid, but still evaporate pretty quickly. Once they get long enough, they start becoming pretty thick and viscous and don’t evaporate pretty quickly at all. Long enough, and they start becoming solid at room temperature and you get paraffin wax.
As this relates to your initial question of how gasoline is different from diesel; gasoline is compromised of shorter chains on average than diesel is. Keep in mind that the actual substances you will encounter in a practical setting have dozens-hundreds of different actual individual chemicals in them that are more complex than simple alkane chains, but this is the general idea behind why they behave differently despite being so similar.
They’re separated from crude oil via fractional distillation; I’m not sure exactly how it works, but it’s basically heating the whole mixture up in a giant container, and then collecting them from different sections of the container as the various densities cause the chains to settle into different layers.
Edit: Changed “fracking” to “fractional distillation”; turns out it’s actually short for “hydraulic fracturing”, which is the technique utilized to extract the crude oil from the ground.
Diesel is an oil and gasoline is a solvent. This means diesel can also provide lubrication as well as combustion and it does this in the high pressure fuel pumps.
If you put gasoline in a diesel vehicle and run it you will remove all lubrication from the diesel pump which will cause it to fail and provide a very expensive issue!
Engines work by making explosions, lots and lots of explosions. That sound you hear when the car is idling? That’s 20 or so explosions every second.
These explosions have to be rather precise, and happen at a certain pace. This is achieved in different ways depending on the type of engine, a gasoline engine will ignite the fuel at the right moment using spark plugs, while a diesel engine will compress the fuel until it ignites on its own.
Using the wrong type of fuel will simply cause the explosions to happen at the wrong times (or not at all), and thus screw up the pace.
I read it as “the wrong kid in the tank”
Was pleasantly surprised it was the right one all along.
The main difference is that gasoline burns easy with a spark, because it is smaller and easily turns into a gas, and diesel burns not so easy with a spark so is compressed with air until it is hot and combusts on it’s own.
As diesel does not burn easy it will not burn at all in a gasoline engine and slowly drown out the engine.
Gasoline in a diesel engine will combust before it should and thus likely break it.
Think of diesel as canola and of gas as perfume. Diesel engines compress air in the cylinders until its very hot then a small amount of oil is injected at high pressure that burns and creates even more pressure, pushing the piston down. Diesel engines are not throttled, that is they are regulated by the amount of fuel injected, not by the amount of air. This is also the reason they will not have good engine braking, hence decompression (jake) braking. Gas engines work by having a vaccum (created by a throttle) in the intake that atomize the perfume-like fuel and mix it with air at a specific ratio (stoichiometric is something like 14.7 parts air to one part pure gasoline). This mixture is then pulled into the cylinder, compressed and then ignited with the help of a spark plug. So if you put diesel in a gas engine, it would not atomize just clog up everything. On the other hand, diesel fuel being oily will function as a lubricant. Putting gas in a diesel engine will mess your injection pump as gasoline is more of a solvent tho I have heard people saying that adding a small amount of gasoline to diesel in winter time helps with starting.
Gasoline and diesel are two different types of fuel. Gasoline is a light petroleum product that is used in spark-ignited internal combustion engines. Diesel is a heavier petroleum product that is used in compression-ignited internal combustion engines.
If you put gasoline into a car that requires diesel, it can damage the engine. Gasoline will not compress like diesel, so it can cause piston and cylinder damage.
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