Internal Combustion Engine/ICE

The concept of the Internal Combustion Engine, or ICE, for powering personal, commercial, and military vehicles is not an expressly human concept, however it is a technology largely maturated and focused on by humanity on Earth over the past century and a half, and drives the vast majority of the world's churning economies.
ICE, in Equestria, though well understood(and even further so, following contact with Earth and humanity), are largely considered a novelty, and are not commercially available to civilians outside of the Griffonic Empire though limited use of the technology has been adopted by various militaries in Equestria, and assorted merchant fleets plying the oceans of the world.
The principles of ICE are relatively simple, fuel is injected into an apparatus, where it is mixed with air(or another oxidizer) to create an appropriately combustible medium, and then ignited by a spark or heat and pressure. Many different types of ICE exist and are in use both on Earth and across Equestria.
Most common fuel sources for ICE are petrochemical fuels such as gasoline, diesel, and kerosene, though thaumaturgically doped biodiesel has begun to spread as a novel ultralow emission 'superfuel,' but its difficulty of manufacture on Earth, and issues with bulk export, has largely limited its utility outside of Equestria.
ICE remains the dominant powerplant technology for vehicles across Earth, despite in recent years, attempts to supplant it with Battery Electric Motor driven systems, and the bevy of local and planetary ecological and climate impacts that have steadily made their presence known as adoption of ICE and its fuel production, has propagated across Earth.

Access & Availability

On Earth, ICE are largely widely available to the average human civilian, commercial enterprises, and the military, though different types of ICE are more, or less restricted in their usage, particularly in regard to certain types of vehicles running on ICE.
On the world of Equestria, ICE is relatively limited in its availability and deployment, with only the Griffonic Empire having a readily available commercial process for the manufacture of, and express demand for, ICE based vehicles and systems in its civilian sectors, however other kingdoms and nations do employ ICE in assorted commercial and military capacities, but do not normally allow personal ownership of ICE vehicles to their general citizenry.