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What are the fuel types for the most efficient rides? We discuss different fuels, from gasoline to ethanol, and how they can impact MPG in cars.

Fuel Types for the Most Efficient Rides

Electric SUV charging
Electric SUV charging

You would be forgiven for assuming the gas-powered internal combustion engine was already toast, given the media coverage and automaker investment into electric vehicles (EV). For example, Stellantis, parent to more than a dozen global automotive brands, recently shared their plans to shell out a whopping $36 BILLION to go all electric in the coming years.

There is no doubt that this battery-powered future is coming soon with the wave of hybrids, plug-in hybrids and full EVs already on dealer lots and slated for production. You can read our article walking through the differences between these vehicle types here, but in the meantime, it is worth remembering that the vast majority of cars and trucks on the road today are still burning dinosaur fuel. Making the question “which are the best MPG cars?”, a highly relevant point of discussion.

Along with gasoline, there a host of fuel types out there that can power your combustion engine, with varying levels of efficiency from diesel and ethanol to synthetic fuel. So, while you await that electrified future, let’s look at what the best bets are for efficiency of existing vehicle fuels.


Gasoline pump
Gasoline pump

Gas is the most readily available and commonly used vehicle fuel, hands down. It is easily combustible making it a favorite of automakers and reasonably efficient depending on what you’re driving. At the moment, that could be a fire-breathing Ford Raptor that guzzles the stuff at a rate of just 15 mpg around town. Or a gas-sipping plug-in hybrid, like the Kia Niro, that blends the fossil fuel past with the battery-powered future and is rated for 46 mpg.

You can buy gasoline in a variety of octanes, depending on engine requirements, a topic you can read more about here, and virtually every vehicle for sale in North America can run on it. Additionally, you will almost never want for a gas station, since they are located in every corner of the United States. As an aside, this abundance of fueling locations shouldn’t lull you into letting that tank run dry as we discuss here. This makes gasoline the benchmark fuel against which all others are measured in the best MPG cars conversation.


Diesel pump
Diesel pump

As the next most commonly used vehicle fuel behind gasoline, diesel is a compelling option if you are focused on efficiency. According to FuelEconomy.gov, diesel fuel contains 10% to 15% more energy than gas, which allows vehicles to travel between 20% and 35% further on a gallon. This makes it ideal for long distance travelling, partially explaining why it is so common in tractor-trailers.

Diesel does require an engine specifically built to burn the fuel, and in the passenger market, the majority of vehicle options are pickup trucks. However, you can find newer Cadillac Escalades and Range Rovers as well as used sedans from German automakers like BMW and Mercedes-Benz that are designed to run on diesel. We dive deeper on the Diesel vs. Gas debate here.


Biofuel pump
Biofuel pump

An interesting option if you already drive a diesel-powered vehicle is biodiesel fuel. Made from vegetable oils, animal fats or recycled cooking grease, biodiesel is a renewable and biodegradable option making it more planet-friendly. It is typically blended with petroleum-based diesel to varying concentrations like B5 (5% biodiesel) or B20 (20% biodiesel).

A standard diesel vehicle can generally tolerate biodiesel, though you will want to consult the owner’s manual for specific automaker recommendations. Fuel economy is slightly lower than petroleum-derived diesel, figure about 2% lower for a B20 blend, but it delivers similar power output along with lower emissions.


Ethanol Biorefinery
Ethanol Biorefinery

Ethanol is a biofuel that is produced using sugar cane, barley, corn and other natural resources. Normally, ethanol is used as additive in gasoline to trim hazardous emissions. In fact, some 98% of gasoline sold in the United States contains 10% ethanol (known as E10) per the Department of Energy. An E10 blend contains about one-third less energy than gasoline so you can expect to see a roughly 4% reduction in fuel economy.

Flex Fuel Vehicles, popularized by Ford in the late 90s, and identified by a FFV or Flex Fuel badge can be operated on E85. This gas-ethanol blend contains between 50% and 80% ethanol, which requires a specially designed powertrain to be burned properly. E85 is not a great option in any search for “best MPG cars”, as using this fuel results in a 15% to 27% reduction in efficiency versus gasoline however, it does cut down on harmful emissions.

Synthetic Fuel

Porsche eFuel plant concept - newsroom.porsche.com
Porsche eFuel plant concept - newsroom.porsche.com

Automakers like Porsche and BMW are reinventing 100-year-old technology to produce synthetic fuel, synfuel for short, as a way to keep internal combustion engines on the road without burning fossil fuel. To create it, electricity generated by wind turbines is used to split water molecules into hydrogen and oxygen. The hydrogen is then combined with atmospheric carbon dioxide, at super high temperatures, to create renewable methanol that can be refined into gasoline and diesel.

Around since the 1920s, this technology historically utilized coal to create the temperatures north of 1500° required, so this new spin using renewable wind is climate-friendly. Porsche has partnered with industrial-giant Siemens to create a pilot program expected to begin soon using the automakers’ vehicles. Data on efficiency is not yet available but certainly, the goal would be to at least match the fuel economy achieved with petroleum-derived gasoline and diesel.

Editor’s Note: This post was originally published in December 2016 and has been completely revamped and updated for accuracy and comprehensiveness.

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Niel Stender

Niel Stender grew up doing replacement work on his 1990 Cherokee and 1989 Starion, so it’s not surprising that he would put his mechanical engineering degree from the University of New Hampshire to use in the car world as a vehicle dynamics engineer. Now engineering sentence structures, his writing infuses his auto experience with his time in marketing and his sales experience. Writing about cars for close to a decade now, he focuses on some of the more technical mechanical systems that are found under the hood and throughout a vehicle.

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