Is the type of gas really important to long superior engine life?

By Shawn Longmore •  Updated: 03/03/22 •  10 min read
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Ever wonder if the type of gas you add to your vehicle matters? This article will help answer questions like this and more. After reading this article, you’ll have a better understanding of common fuel types, the average octane difference between types of gas, and the pros and cons of each.

Types of Gas

There are three main categories of gas types: Regular or Unleaded (low-grade), Plus (mid-grade), and Premium or Super Unleaded (high-grade), which have all been around since the early 1900s. There’s also Diesel fuel, but it’s different, and you should never use it in gasoline engines. Today, we also have E85 (flex fuel), making it difficult to know the best type for your motor.

Understanding Octane Ratings

The octane levels determine how well an engine can mix the air and fuel. Higher numbers mean more power, better fuel efficiency, and fewer chances of knocking sounds.

In the United States, we have gas with octane levels of 85 to 94, depending on the state and elevation. So if you live in higher elevations, you’ll typically have lower octane ratings than states at lower elevations.

So what’s the difference in octane levels? A higher number means the gasoline has additional oxygen blended with it, making the mixture of air and gas burn faster and easier, so you get more power from less fuel. Below are more details for each type of gas, along with some pros and cons.

Unleaded or Lower-Octane Fuel

Unleaded or regular gasoline typically has the lowest octane rating, and it’s the most common form of gasoline available today. You’ll find this grade of gasoline listed as 87-octane fuel.



Plus or Mid-Grade

Mid-grade gasoline has an octane rating between 88 and 90. The extra oxygen helps make this gas more powerful than regular unleaded. As a result, it’s slightly more expensive than regular unleaded, but it’s still cheaper than premium grades.



Premium or Super High-Octane Fuel

Premium or Super Unleaded gasoline is considered Higher-Octane Fuel and has an average of 91-octane or higher. It’s the highest quality fuel available and often used by race teams and enthusiasts because of its ability to produce more horsepower. Premium fuels also provide better performance in cold weather conditions.



E85 or Flex-Fuel

This type of gas is a blend of 85% ethanol and 15% gasoline, allowing your vehicle to use either gas or ethanol. We’ll discuss ethanol a little later in this article. The price of corn determines the price of E85, which causes it to fluctuate more than traditional gas at times.

According to the historical price chart put out by, corn prices are roughly $7.2575 per bushel. As a result, E85 costs about 21 cents per gallon less than regular unleaded gas when writing this article.

E85 isn’t as available as other fuel types since it has fewer filling locations across the United States. However, according to the U.S. Department of Energy, roughly 3900 gas stations across the U.S. provide E85.



Diesel Fuel

Unlike other fuel types, diesel fuel has a lower octane level of 25 to 40 and is heavier than any other type of gas. Therefore, accidentally adding diesel fuel to a gasoline engine can lead to issues with your pistons, spark plugs, and valves. In some cases, having too much diesel fuel in a gas motor can lock your cylinders. Along with causing damage to the engine, diesel fuel can also destroy your catalytic converter.

Diesel fuel might be bad for vehicles that require other types of gas, but it’s excellent for cars designed to run on it. Below are some of the pros and cons of diesel fuel when used in the correct type of vehicle.



Alternative Fuel Types

There are roughly six other sources to choose from besides the ones listed above. These include electricity, natural gas, propane, hydrogen, biodiesel, and ethanol. Each one offers its own set of advantages and disadvantages. So let’s take a closer look at each type to understand better which alternative fuels will work best for you.

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Services & Products to Help Improve Engine Life

Below is a list of services we feel help improve the life of your engine when performed at the recommended intervals within the owner’s manual. But, of course, we’re not mechanics and recommend checking with a professional for detailed recommendations for the vehicle you drive.


Final Thoughts

You should check the owner’s manual for your vehicle to determine which type of gas it requires to help it last longer. If you’re not driving a high-end luxury car or sports car, chances are you’ll have no problems using low-grade or regular unleaded gas. Be sure to check your owner’s manual or the sticker on the inside of the door to your gas cap to determine which type of gas is best for your vehicle.

Shawn Longmore

Shawn is the founder of Auto Glass Locator and enjoys providing articles related to automotive parts and services. His mission is to make it easy for everyone to find all the information they need in one spot. Each year he continues to help more people find great deals on auto glass and other automotive services.

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