Internal Combustion Engine

Internal combustion engines are machines that convert chemical energy of fossil fuels to kinetic energy. When linked to drivetrains , they can propel vehicles . Whether such an engine is present on a vehicle, is a defining characteristic of its powertrain .

To run a vehicle with an internal combustion engine, the fuel is typically stored in fuel tanks carried onboard. Vehicles with engines also carry and use oil to lubricate the engine, and sometimes other mechanisms . The level of both resources can be monitored by gauges, usually found in the vehicle's cab , and they both need to be periodically refilled .

Starters are commonly used to start engines. A starter is a small electric motor that spools the engine until it starts combusting fuel and running on its own. It is usually controlled by a switch, a key, or a button, found in vehicle cabs or engine bays. For the starter to function, a respective breaker must be enabled.

Each engine start creates some wear on it , and so does mere running. This is normal, due to wear and tear of the moving parts. It is generally less economical to frequently turn the engine on and off, than to keep it idling for several minutes.

Rotational speed of an internal combustion engine, measured in rotations per minute (RPM), is controlled by throttle . Throttle position sets the desired engine RPM, while a device called the governor automatically adjusts fuel injection in order to achieve that goal. With variations in engine load, the fuel consumption will vary, regardless of the current RPM.

There is a range of rotational speeds that engines are designed to operate in. The minimum RPM is the speed at which the engine runs on its own, or idles. Going any slower that that causes insufficient combustion rate and the engine can shut down, or stall. The maximum RPM is marked by a red line on the RPM gauge, and can be reached by giving too much throttle, or with faulty operation of a transmission . Going any faster than that leads to engine damage , which may be catastrophic.

Internal combustion engines have a specific RPM at which they produce peak power output. Below and above that RPM, the power output diminishes. The peak power output is usually slightly below the maximum RPM. It is generally most efficient to run engines at high RPM when accelerating or engine braking , and at low RPM when coasting.

To stop an engine, its fuel supply needs to be cut. This is usually done by a handle or a button labeled "fuel cutoff", which may be located in or out of the vehicle.

Since vehicles with internal combustion engines carry fuel onboard, they may explode if exposed to fire , or other explosions . They also emit harmful particles to the atmosphere, contributing to the environment damage by mere running.

Internal combustion engines in vehicles can drive drivetrains directly, such as with diesel-mechanical and diesel-hydraulic powertrains, or they can drive generators that produce electrical power, as is the case with diesel-electric powertrains.