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E-85 vs. E-15 vs. E-10 (All Differences Explained!)

E-85 vs. E-15 vs. E-10 (All Differences Explained!)

We’ve written extensively about different fuels and what cars should and shouldn’t use them. However, one question we haven’t answered is what the actual differences and similarities are between E-85, E-15, and E-10. Here’s a quick answer:

The difference between E-85, E-15, and E-10 is the percentage of ethanol used. E-10 uses 10% ethanol, E-15 15% and E-85 uses 51 – 83% ethanol. Furthermore, E-10 and E-15 typically have an octane rating of 87 – 95, whereas E-85 typically has more than 100. Therefore, E-85 produces 20-30% more horsepower, but it is also 20-30% less efficient.

However, that certainly doesn’t answer the question wholly. Below, we’ll first start with a quick introduction to these types of fuels and their characteristics. Furthermore, we’ll discuss the six differences between these types of gasoline. We’ll also discuss what cars can use what type of gasoline and if it’s a good idea to mix them. Read on!

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What Do The Letters And Numbers Indicate?

In North America, you can buy different kinds of fuels. E-85, E-15, and E-10 are all options you will encounter. Therefore it’s good to know what these abbreviations stand for.

The ‘E’ in these abbreviations stands for ethanol. According to the U.S. Department of Energy ‘Ethanol is a renewable, domestically produced alcohol fuel made from plant material, such as corn, sugar cane, or grasses

The number in the abbreviation initially stands for the percentage of ethanol mixed with regular gasoline. E-10 is gasoline blended with 10% ethanol. E-15 is gasoline mixed with 15% ethanol. However, E-85 is not 85% ethanol. Ironically, E-85 contains 51 – 83% ethanol, depending on the region and the season you buy it.

This odd difference is that E-85 does have 85% ethanol in other parts of the world (such as Australia). However, weather differences in the Northern part of the globe dictate that 85% ethanol can’t always be used, and therefore the percentage is changed, but the name is kept the same.

Also read: Can You Mix E-85 And Unleaded Gasoline? (Explained)

What Cars Can Use E-85, E-15 and E-10

As a general rule of thumb, all cars can run on E-10 gasoline. This is because a lower percentage of ethanol is never a problem.

E-15 can only be used in gasoline vehicles made after 2001. This kind of fuel was first introduced in 2011 in the United States because its production emits fewer greenhouse gases than regular gasoline (more on that later).

E-85 can only be used in so-called ‘Flex Fuel’ cars. Flex Fuel cars have a fuel system designed to use E-85 gasoline. In general, these cars will have badges or markings on the car, which notifies you of the potential use of E-85. See the image below.

Comparing E-85 to E-15 and E-10

All types of gasoline come with distinct advantages and disadvantages. Below, we’ve listed six factors that will show us the inherent differences between these fuel types.

Octane Rating

One of the most significant differences between these three types of gasoline is the octane rating. Octane is a measure of how stable the fuel is. The higher the octane number, the more pressure the fuel needs to ignite, the more mechanical power it provides, and the more horsepower the car produces.

Both E-10 and E-15 can have varying octane ratings. However, most of these types of gasoline are sold with an octane rating of 87 – 95. This is because this is the octane rating most cars are designed to use, and there’s no need for commercially available gasoline with a lower or higher octane rating.

On the other hand, E-85 has an octane rating of 100 – 113 (assuming it has 85% ethanol). This has some distinct advantages for certain kinds of cars (we’ll get into that in a moment) but it’s not suitable for all cars.

Also read: How Much Ethanol In 87 – 93 Octane Gas? (Regular & Premium)


The higher octane rating of E-85 means the gasoline creates more mechanical power, which results in more horsepower. Compared to regular and premium gasoline with an octane rating of 87 – 93, E-85 makes 20 – 30% more horsepower (assuming 85% ethanol, which will not be the case in the United States).

If the fuel does contain 85% ethanol, there’s a high chance it’s used in car racing. This is a widespread occurrence in Australia.

Fuel Economy

The fact that E-85 is more stable, and produces more power, also means that it’s a lot less economical. E-85 that’s sold in the United States generally makes the MPG drop by 20 – 30% compared to regular or premium gasoline that’s mixed with 10 – 15% ethanol.

However, people in favor of biofuels (which is what E-85 is) have stated many times that there are engines that have shown to be 20% more effective running on E-85 than other gasoline. They blame car makers for not designing the right engine and modifying gasoline engines to make them work with E-85, whereas a modified diesel engine would work much better.

Also read: 7 Differences Between E-85 And Bio-Diesel


However, the drop in fuel economy is made up for because E-85 is typically more than a dollar per gallon cheaper than 87 octane gasoline, and about one and a half dollars per gallon cheaper than 93 octane gasoline (whether these types of gasoline have 10 – 15% ethanol barely matters)

In conclusion, E-85 is around 20% cheaper than regular octane gasoline and 20 – 30% less effective in fuel economy. This means the differences between price and MPG even out over the long run.

Also read: Is E-85 Cheaper To Use Than Other Gasoline? (Explained)

Maintenance And Lifespan

One disadvantage of the use of ethanol is the fact that it’s a very corrosive substance. This is not that much of a problem for E-10 and E-15 gasoline. However, it is for E-85 gasoline. There’s no denying that cars that run on E-85 need more maintenance and more frequent checkups of certain vehicle parts. These include the spark plugs, valves, and fuel lines of the fuel system.

This is because these elements have a much higher wear-and-tear when using E-85. If you run your car on E-85 or plan on doing so, we highly advise you to check your car’s maintenance schedule. If your car is made for use with E-85, the carmaker will have published a maintenance schedule specific to E-85 vehicles.

Emissions & Environmental Impact

The final factor we need to discuss is the emissions created by the different types of gasoline. Many people assume that E-85 vehicles are cleaner because they burn bio-fuel. However, studies around this subject are inconclusive. This is mainly because of the vast number of variables in play during the research (the type of car, engine, percentage of ethanol, conditions, etc.). Because of this, we can’t make hard conclusions about this.

However, E-85 emissions are considerably lower when we compare them to regular gasoline (E-10 and E-15) on a life-cycle basis. This is because E-85 is much more environmentally friendly to produce (because it contains more ethanol), and the crops that are grown also take in carbon dioxide when they’re still on the field. According to the US Department of Energy, emissions of E-85 that are based on corn are 40% lower than the emissions of regular or premium gasoline (both E-10 and E-15), making E-85 the superior choice.

Also read: Why Mixing Different Octane Gasoline May Destroy Your Car


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