Writing about different types of fuel is a daily practice on this blog. However, we haven’t answered every question yet. Therefore, we will use this blog to talk about how much ethanol is in gasoline with different octane ratings. Let’s start with a quick answer:
In the United States, gasoline with an octane rating between 87 – 93 has 10 or 15% ethanol. These types of gasoline are referred to as E-10 and E-15. On the other hand, E-85 typically has an octane rating of 94 or higher.
However, that doesn’t answer the question wholly. Below, we’ll first explain how much ethanol is in each type of gasoline more thoroughly. We’ll also discuss why these percentages are chosen and why this number has increased. Furthermore, we’ll also discuss how much ethanol is in E-85 and the differences between E10, E15, and E85. Finally, we’ll see which type of gasoline is best for your car. Read on!
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How Much Ethanol Is In Each Type Of Gasoline And Why?
As we said in our introduction, gasoline with an octane rating of 87, 88, 89, 90, 91, 92, or 93 has an ethanol percentage of 10 or 15%. However, why does the gasoline sold not contain a lower or higher rate, and why did we settle at these numbers.
Cleaner Than Regular Gasoline
Ethanol is mixed into gasoline because it is cleaner than gasoline entirely made from gasoline. Congress first mandated the use of ethanol in gasoline in 1990 in the Clean Air Act, and in 2005 Congress passed the Renewable Fuel Standard, which meant a minimum level of ethanol had to be present in gasoline.
However, contrary to popular belief, there’s no scientific evidence for ethanol burning cleaner than regular gasoline. Scientific studies so far have been inconclusive. However, we know that creating ethanol (made out of plants such as sugar cane and corn but don’t try to actually put sugar in your tank) is much cleaner to produce. Furthermore, the plants take up CO2 when they’re growing, which means that ethanol is 40% cleaner than regular gasoline on a lifecycle basis.
Furthermore, E-10 and E-15 have existed ever since they were introduced because it creates many jobs. For example, Iowa can trace $5 billion per year and 47,000 jobs back to ethanol production for gasoline. Since Iowa is a critical state, political candidates have been sure to promote ethanol in gasoline.
Politics are also the reason why both E-10 and E-15 exist. When ethanol was first introduced in gasoline in 1990, it started with 10% ethanol.
However, in 2007 Congress raised the levels of the Renewable Energy Standard (which they had signed in 2005). This meant that they aimed to sell 36 billion gallons of ethanol by 2022. As a result, carmakers were forced to start creating cars that we could run on 15% ethanol instead of the 10% they used before.
When you read the owners manuals of different generations of the same car, owners manuals created after 2012 will say that the car is suitable for 15% ethanol whereas before it was 10%.
Can 87 – 93 Octane Also Be E-85?
One thing we’ve failed to mention so far is the existence of E-85 gasoline. As the name suggests, this is gasoline with a much higher ethanol percentage than regular E-10 or E-15. However, it doesn’t have 85% in the United States.
In other parts of the world, E-85 generally does have 85% ethanol. However, in North America, E-85 has to be adjusted for seasonal differences (otherwise, cars wouldn’t start because ethanol is difficult to ignite at low temperatures).
E-85 sold in the United States has 51 – 83% ethanol, depending on the region and time of year. But does this also mean it can be an 87 – 93 octane gasoline?
The chance of E-85 having an octane level below 93 is very slim. This is because ethanol has an octane rating of 100 – 113. For simplicity, the ethanol we use has an octane rating of 100.
Manufacturers of gasoline then have to mix this with regular or premium gasoline with an octane rating between 87 – 95. Our ethanol has 49% regular gasoline with an octane of 87 and 51% ethanol with an octane of 100.
(49% x 87) + (51% x 100) = gasoline with an octane rating of 93,63. In other words, it’s impossible (or at least very unlikely) for E-85 to have an octane rating below 93.
- E-85 Flex Fuel vs. 87 Octane (Differences & Similarities)
- E-85 Flex Fuel vs. 91-93 Octane (Differences & Similarities)
- Can You Mix E-85 And Unleaded Gasoline? (Explained)
Differences Between E10, E15, and E-85
Furthermore, it’s essential to know the differences between these three commercially available gasoline types. There are many; if you want to know all the ins and outs, please read this article: E-85 vs. E-15 vs. E-10 (All Differences Explained!). Right now, we’ll give you a quick summary:
- E-85 is harder to ignite which means it produces more mechanical power and therefore more horsepower than E-10 and E-15.
- E-85 is typically 20% cheaper than regular gasoline (E-10/15).
- However, E-85 is also 20 – 30% less fuel efficient which means the price benefit is neutralized by the worse fuel economy.
- Cars that run E-85 adhere to a different maintenance schedule that typically involves a little more work.
- However, E-85 gasoline creates 40% fewer emissions than regular gasoline (E-10/15).
How Much Ethanol Should Your Car Take?
Whether or not your car can run on E-10, E-15, or E-85 octane and which one would be the best option depends on several factors.
First, you’ll have to know what car you have and what gasoline the carmaker prefers. This information is mentioned in the owner’s manual. On the other hand, you can also search on this website by typing in ‘car model + gas’ in the search bar. We’ve written an article for almost every type of car sold in the United States.
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.
Most of the time, E-85 is used in cars with a large engine with many horsepowers.
It’s good to know that 82% of cars sold in the United States can use E-10 / E-15 with an octane rating of 87 gasoline. This is the most used fuel for lower and mid-segment cars, SUVs, and trucks. However, some cars can’t run on this type of fuel, and it will result in ‘engine knock’ (a loud banging noise from the engine.
If you have a premium brand car, a sports car, a car with a turbocharger, or any car with a larger than average engine, it’s wise to check your owner manual. Your car will be able to take either E-10 or E-15. However, it’s likely it also needs 91 octane or higher.
Furthermore, if your car needs 87 octane, it’s not wise to fill it with premium gasoline. This is because the engines aren’t made for this type of fuel. They will be able to run on it without any problems; however, you won’t gain any benefit, and it will only cost you more.
Hi! My name is Stefan; I’m the owner and lead writer at TheDriverAdviser.com.
I’m an active writer on this blog myself, as well as a novice car mechanic. For the really technical stuff, I find writers with experience as a mechanic or who have studied mechanical engineering.
Read more about our fantastic team on our about page!