The size class is determined by the US Environmental Protection Agency. The size class for cars is determined by the interior passenger and cargo volumes. The size class for trucks is defined by the gross vehicle weight rating (GVWR), which is the weight of the vehicle and its carrying capacity.

EPA estimates for fuel efficiency (measured on a mile-per-gallon basis) are based on laboratory tests conducted by manufacturers according to federal regulations. EPA re-tests about 10% of vehicle models to confirm manufacturers’ results.

An engine’s displacement is the total volume of the engine’s combustion chambers, a rough index of the engine’s size and power. This is typically measured in liters (3.2L, for example), though sometimes it is expressed in cubic inches. I-4 and V-6 refer to the configuration and number of cylinders.

The transmission adapts the output of the engine to the drive wheels. Transmissions usually have multiple gear ratios (“gears”) with the ability to switch between them as speed varies (6 gear ratios = “6 Speed”). Transmissions must either be controlled manually by the driver (“Manual Transmission”) or automatically by the vehicle (“Automatic Transmission”). One type of Automatic Transmission is the Continuously Variable Transmissions (CVT) which doesn’t have a fixed number of gears.

The drivetrain of a vehicle is the group of components that deliver the engine’s power to the drive wheels. Common configurations include front-wheel drive, rear-wheel drive, four-wheel drive and all-wheel drive.

The number of people the car will hold.

A unit to measure the power of engines.