antiknock
/ˌæntiˈnɑk/
noun
- A substance added to fuel to prevent engine knocking (a pinging sound caused by premature combustion).
- The mechanic explained that the right antiknock can improve engine performance and reduce noise.
- Modern cars use unleaded fuel with special antiknock additives to protect the engine.
- Lead was once a common antiknock in gasoline, but it is now banned in most countries.
adjective
- Designed to prevent or reduce engine knocking.
- High-octane fuel has better antiknock properties than regular gasoline.
- Some older engines require antiknock additives to run smoothly.
- The antiknock rating of a fuel is measured by its octane number.