When one thinks of subcompact cars, eco-friendly, minimalist, and incredibly cheap vehicles come to mind. One of the many benefits of a subcompact car is stellar gas mileage, typically in the 30-40 mpg range. Government institutions rate manufacturer offerings to provide more information to the public on fuel economy and other priorities. However, the Environmental Protection Agency (EPA) seems to have quite an interesting way of defining a subcompact car.

How does the EPA define subcompact?

Automaker designations aside, the EPA has its own classification system for vehicles. Federal Regulation, Title 40—Protection of Environment, §600.315-08 “Classes of comparable automobiles,” defines a range by interior volume index.

• Minicompact: Less than 85 cubic feet
• Subcompact: 85 cubic feet but less than 100 cubic feet
• Compact: 100 cubic feet but less than 110 cubic feet
• Midsize: 110 cubic feet but less than 120 cubic feet
• Large: More than 120 cubic feet

Despite what type of car a manufacturer says it is, the EPA could define it in a completely different class. Sometimes, those definitions don’t make sense with their results and lead to shocking results for the thirstiest subcompact.

Which subcompact did the EPA rate with the worst gas mileage?

Considering the above chart, it’s surprising to see what fits into those interior space limitations. Therefore, the subcompact that achieved the worst gas mileage wasn’t an affordable small sedan with a wheezy four-cylinder. No, it was a Bentley Continental GT Speed.

Yes, that’s correct. The Bentley Continental GT Speed’s 87 cubic feet of interior space puts it in the EPA subcompact class. It also has a rather low trunk volume of just 11 cubic feet. Nevertheless, it should be enough for a shopping day on Rodeo Drive.

Bentley Continental GT Speed fuel economy

When creating their best and worst fuel economy chart, the EPA uses combined gas mileage. With a city mpg figure of 12 and 20 mpg on the highway, the Bentley gets a combined 15 mpg. It’s nearly half the EPA’s 2023 vehicle average of 28 mpg. Yet, that’s to be expected when there’s a 6.0-liter twin-turbocharged W12 under the hood.

Although it weighs well over two tons, the 650-horsepower GT Speed doesn’t just turn fuel into noise; it’s immensely fast. Car and Driver estimates they can launch the mammoth to 60 mph in just 3.1 seconds.

What does it cost to fill up the GT Speed? 

According to the EPA, Bentley Continental GT Speed owners will spend much more on fuel than those driving a vehicle at or above the EPA average. The government agency says it will cost $11,500 more over the course of five years.

Since the GT Speed takes premium fuel, the EPA estimates it will cost $6.77 to drive 25 miles. That could be because the traffic on the 405 is so bad. But that shouldn’t matter for potential buyers of a car with a starting MSRP of $291,225. However, that’s only for the coupe; the convertible is another $26,000, and that’s before the opulent options list.