Internal-combustion engine and Petrol engine

Internal-combustion engine noun - A heat engine in which combustion occurs inside the engine rather than in a separate furnace; heat expands a gas that either moves a piston or turns a gas turbine.

Petrol engine and internal-combustion engine are semantically related. In some cases you can replace phrase "Petrol engine" with "Internal-combustion engine", this phrases are similar.

Petrol engine noun - An internal-combustion engine that burns gasoline; most automobiles are driven by gasoline engines.

Internal-combustion engine and petrol engine are semantically related. Sometimes you can use "Internal-combustion engine" instead a noun phrase "Petrol engine".