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Different Types of Fuel and What’s Best for Your Car

New types of fuel are emerging, but is gasoline still your best bet?

types of fuel

It wasn’t too long ago that gasoline and diesel were the only two options to power your car. But these fuel types come with serious drawbacks including high cost and environmental hazards. With the increased need to use renewable fuel sources, several other options are being used more frequently – and more are continuing to emerge. With that in mind, here are a few of the most popular types of fuel for cars, and how to determine the right one for your vehicle.


The most commonly used fuel for cars is gasoline. It is easily combustible, which allows for quick starting and fast acceleration. However, the high levels of carbon dioxide produced from burning gasoline is a leading contributor to pollution and, in turn, global warming. According to the Union for Concerned Scientists, cars and trucks account for nearly one-fifth of all U.S. global-warming emissions. In response, many companies and consumers are increasing their use of alternative fuel types.

There are generally three different types or “grades” of gasoline, determined by the gasoline’s octane level. A level of 87 is considered “regular,” 91 is “premium,” and 89 is mid-grade. The grade of gasoline you should use depends on the type of vehicle and engine you have. (More on that below).


Along with gasoline, diesel is the other popular form of fuel, used specifically for diesel engines. Diesel vehicles are more fuel efficient, often traveling about 20% to 35% farther on a gallon of fuel than their gas-powered counterparts. Therefore, vehicles that are travelling far distances, such as trucks and vans, commonly use diesel engines. It also produces less carbon dioxide than gasoline. However, it does create nitrous oxide, which causes smog.

Liquified Petroleum

Better known as propane, liquified petroleum is a much cleaner and cheaper form of fuel. Many hybrid cars in foreign countries such as the United Kingdom have been designed to use propane. However, automobiles in the United States rarely use it. The only way to use propane domestically is to convert your vehicle’s gas engine.

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Ethanol is a popular biofuel made from sugar cane, barley, corn and other natural resources. However, it is generally used as an additive in other fuel sources in order to help cut down on hazardous emission. According to the U.S. Department of Energy (DOE), more than 98% of U.S. gasoline contains ethanol, typically E10 (10% ethanol, 90% gasoline).

But gasoline with higher percentages of ethanol also exist. E85, also called flex fuel, is an ethanol-gasoline blend containing 51% to 83% ethanol. E85 can only be used on Flex Fuel Vehicles, which are specially designed to run on gasoline, E85, or any mixture of the two. Ethanol can be extremely helpful in cutting down on emissions but a car’s fuel delivery system and engine need to be designed to use it.

Compressed Natural Gas

Compressed natural gas is a clear, odorless and non-corrosive gas that can be used in liquid or gas form to run a combustion engine, though gas engines would need to be converted to use it. The fuel produces approximately 80% less emissions than gasoline. Additionally, vehicles that run on compressed natural gas are similar in power, acceleration, and cruising speed to gasoline or diesel vehicles. Compressed natural gas can limit driving range, though, as less overall gas can be stored in the same size gas tank.


This renewable, biodegradable liquid fuel is made from vegetable oils, animal fats or recycled cooking grease. According to the DOE, biodiesel emissions are 74% lower than those from petroleum diesel. Diesel vehicles can generally use a low percentage of biodiesel without any engine modification. However, higher levels of the fuel will require modifications.

types of fuel

Determining the Type of Fuel for Your Car

Gasoline vs. Diesel

Most vehicles in the United States run on gasoline or diesel fuel. The driver’s manual should dictate the fuel type your car needs. There should also be a label on the fuel door that reads something along the line of “Diesel Fuel Only” or “Unleaded Gasoline Only.” If there’s ever a doubt, call the manufacturer.

It is imperative that you put the proper fuel in your car’s tank. Gas engines cannot combust diesel fuel and vice versa, so the car won’t start if it is filled with the wrong fuel type. Even worse, it can cause serious damage to the engine.

AAA Approved Auto Repair Facilities can help get your car back out on the road. Find the nearest one here.

Regular vs. Premium

As stated previously, gasoline grades are dependent on the fuel’s octane level. Higher octane levels ensure the gas burns evenly, which helps keep your engine cleaner and improve performance. Therefore, it is commonly used in vehicles with high-compression engines or turbochargers, like sports cars.

The car’s manual should state the gasoline grade needed. It may suggest premium gas but not require it. If this is the case, your car should be able to run fine with lower grade gas, and it could save you money.

Alternative fuels

While gasoline and diesel are the most common and readily available types of fuel for cars, in most cases, any vehicle can be converted to use an alternative fuel source. Engines can be modified to either operate exclusively on one alternative fuel or to have two separate tanks and fuel systems – one for conventional fuel and another for an alternative fuel. Converting your engine would cause some upfront costs but should save you money in the long run. With increasing gas prices, alternative fuels present an inexpensive option.

AAA members can save money at the pump with Shell’s Fuel Rewards program. Learn more.

Motorists can find the cheapest gas prices wherever they are by using the AAA Mobile App.


    I was disappointed that you failed to warn readers of the dangers to small engines of using Gasoline containing Ethanol. I believe this now an undisputed problem – the denial is therefore usually political. Can you please enlighten me?
    Thank you,
    Geoffrey Brookman.
    PS. I am fortunate to live in a state where no -Ethanol fuel has limited availability rather than none.

    • Andrew S.

      Hi Geoffrey, thanks for the comment. We tried to keep the focus on car engines but you are correct about ethanol’s effect on small engines. Here is a response from our Car Doctor, John Paul: In small engines such as lawnmowers and other power equipment, higher concentrations of ethanol can be very corrosive to carburetors. In addition the higher concentration of ethanol can cause hotter running conditions and potential engine failure. At AAA we believe that ethanol can help us continue toward energy independence, but the fuel delivery system and engines need to be designed to use it.

  • FRED E.

    Saying that ethanol can be used in cars designed for gasoline is misleading and potentially costly advice to your members. If a car is not designed for so-called flex fuel (E85), the gas tank and fuel line components can be severely damaged. Seeing as most gas stations sell E85, this article implies that it would be ok to use in any gas powered car. You should clarify and issue a correction

    • Andrew S.

      Hi Fred, you’re absolutely right–it was misleading. We have updated the article to include flex fuel. Thanks for your input!


    Great topic, but you forgot to include all of those items like the lawn mower, tiller, weed wacker, etc. Using Ethenal in the gas can screw up the carburater in just 1 season.

    • Andrew S.

      Hi Richard, we were trying to keep the focus on car engines but you are certainly right — ethanol can damage smaller engines. Thanks for your input!

  • johnm304

    I am really disappointed that this article did not cover the king of the alternate fuels — electricity. None of the fuels covered have matching passenger vehicles from the major manufacturers. But electric vehicles (EVs) are available from several automakers. First generation EVs are excellent commuter vehicles and the second generation EVs have over 200 miles of range and can charge in the time it takes for a road trip “bio break”. I hope the omission of EVs from this article was accidental and does not reflect a bias in favor of fossil fuels.


    Excellent presentations, comments and “debates”.. especially useful for those of us who simply start the car and drive. Thanks

  • I have a 1.4L intercooled turbo engine and the manufacturer states that premium is recommended. I have been using premium but could I get away with a lower octane gas ? Thanks

    • Andrew S.

      Hi John, here is an answer from our Car Doctor John Paul:

      AAA has performed extensive testing on vehicles where it is recommended,not required, that premium fuel is used. What we have found in almost every case there was no difference in performance and fuel economy. In the cases where there was a slight drop in fuel economy, the cost savings of regular fuel over premium fuel offset any slight drop in fuel economy.

      Of course if your car requires premium fuel, you need to use it.

      In my own personal testing I have never noticed any differences in performance or fuel economy.

  • DAVID W.

    A reference to Top Tier-graded gasoline would be helpful. I’ve read Consumer Reports’ discussion of it and it seems like the best choice.

  • Completely agree with johnm304’s comments on this article from August 2019. Unfortunate that a year and a half later, this article has not been updated, even with the rise in electric vehicle (EV) sales and automakers signaling a shift to EVs. I took a 7500 mile road trip across North America in 2019 in my EV and will never go back to gasoline. EVs are just better cars.

  • George F.

    Regarding the Octane Level: what is the down side of running Regular Gas (87) instead of High Octane 93? 2nd questions: Are you damaging the engine?


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