The shift toward ethanol blending is a major talking point in the automotive world today.
While it is often promoted as a way to reduce emissions and save money on fuel imports, the reality is much more complicated for people driving older vehicles.
If you own a car that is ten years old or older, it was likely built at a time when E5 or E10 was the standard.
Introducing E20, a mixture that is 20% ethanol, into these older systems is like asking a marathon runner to perform on a diet they aren’t used to, eventually, things will start to break down.
E20 has disadvantages that are more noticeable in cars that are ten years old and older.
Eating Away at Metal Parts (Corrosion)
The first and most serious issue is corrosion. Ethanol is a type of alcohol and alcohol is naturally corrosive to certain materials.
In cars built a decade ago, many parts of the fuel system were made from metals like aluminium, brass, and zinc-coated steel.
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When E20 fuel sits in your tank or moves through your fuel lines, it begins to chemically react with these metals.
Over time, this creates a white, powdery residue or rust-like flakes. These flakes don’t just stay in one place, they travel through the fuel system and can cause blockages or, worse, eat holes through your fuel tank or lines.
For an older car, this means the engine is constantly under attack from the inside out.
Destroying Rubber and Plastic
Inside your car’s engine and fuel system, there are hundreds of small rubber seals, O-rings, and plastic hoses.
Their job is to keep the fuel moving where it should and prevent leaks. Ten years ago, the rubber used in these parts was not designed to handle high levels of alcohol.
Ethanol acts as a solvent. When it comes into contact with older rubber, it causes the material to swell up and become soft
Eventually, the rubber loses its shape and starts to rot or crack.
This leads to fuel leaks. A fuel leak is not just a waste of money, it is a major fire hazard.
In an older car, these hoses are already aged by heat and time and E20 fuel simply speeds up their inevitable failure.
Loosening Old Dirt (Clogging)
One of the hidden dangers of E20 is that it is actually too clean in the wrong way.
Because ethanol is a powerful solvent, it cleans the inside of your fuel tank.
You might think this is a good thing, but in a ten-year-old car, there is a lot of dirt, varnish, and sediment that has settled at the bottom of the tank over the years.
When you pour E20 into the tank, it acts like a scrub brush. It loosens all that old dirt and sends it flying through the fuel lines.
This massive wave of debris quickly reaches the fuel filter and the fuel injectors.
When the injectors, which have tiny holes, get clogged, the car will sputter, lose power, or refuse to start. Instead of a clean engine, you end up with a system choked by its own old waste.
Poor Fuel Economy
This is the disadvantage you will notice most in your wallet.
Ethanol contains significantly less energy than pure gasoline.
Specifically, ethanol has about one-third less energy per gallon. When you increase the blend to 20%, you are effectively watering down the punch that the fuel gives your engine.
Because there is less energy in every drop of fuel, your engine has to burn more of it to maintain the same speed and power.
You will find yourself visiting the gas station more often.
Even if E20 is slightly cheaper at the pump than regular gas, the drop in mileage (how far you can drive on one tank) usually means you end up spending more money in the long run.
You are paying for a fuel that simply doesn’t take you as far.
The Water Problem (Phase Separation)
Ethanol is hygroscopic, which means it pulls moisture out of the air.
In a place with high humidity, moisture gets into your gas tank through the vent system. In regular gasoline, a little bit of water isn’t a huge deal. But with E20, it’s a disaster.
Once the ethanol in your tank absorbs enough water, it undergoes something called phase separation.
The ethanol and water bond together and become too heavy to stay mixed with the gasoline.
This heavy, watery mixture sinks to the bottom of your tank. Since your engine draws fuel from the bottom, it ends up sucking in a gulp of water and alcohol instead of gas.
This can cause the engine to stall instantly and can lead to permanent damage to the engine’s internal parts.
Trouble Starting in the Morning
Gasoline is designed to evaporate easily so that it can catch fire inside your engine.
Ethanol does not evaporate as easily, especially when it is cold. In an older car, the computer and the fuel system are tuned for the evaporation rate of standard gasoline.
When you try to start your car on a cold morning using E20, the fuel doesn’t turn into a vapour properly.
This results in hard starting, where you have to turn the key or press the button multiple times before the engine catches.
This puts a massive strain on your battery and your starter motor. Over time, trying to force an E20-filled engine to start in the cold will wear out these expensive electrical parts.
Thinning Out the Oil
Engine oil is the lifeblood of your car. It keeps the metal parts from rubbing together and melting.
However, E20 can interfere with this. When an engine isn’t designed for high ethanol, it doesn’t always burn the fuel completely.
Some of that unburnt E20 can leak past the pistons and mix with the oil in the crankcase.
When ethanol mixes with oil, it thins the oil out and breaks down its ability to lubricate.
This is called fuel dilution. If your oil becomes too thin, it can’t protect the engine’s bearings and moving parts.
You might not notice it immediately, but your engine will begin to wear down much faster than it should, leading to a much shorter lifespan for the vehicle.
Exhaust and Sensor Damage
Modern cars use sensors to sniff the exhaust and tell the engine how to run.
They also have a catalytic converter to clean up pollution. Older cars have these too, but they are more sensitive.
Because E20 changes the way the fuel burns, it changes the chemicals in the exhaust.
The extra heat and the different chemical byproducts of E20 can coat the oxygen sensors in soot or poison the precious metals inside the catalytic converter.
Once the catalytic converter is damaged, your check engine light will come on and your car will fail any emissions test.
Replacing a catalytic converter is often one of the most expensive repairs you can do on an older car—sometimes costing more than the car is worth.
While E20 might seem like a modern solution for a greener future, it is a dangerous choice for a car from the mid-2010s or earlier.
The corrosive nature of the alcohol, the risk of water contamination and the physical heat damage to the engine make it a risky gamble.
Moving to E20 might save a few cents today, but it could cost you your entire car tomorrow.
