Pushing an engine to the highest revolutions per minute (RPM) it can safely sustain before internal components risk catastrophic failure. The term comes from the literal red line printed on the tachometer gauge. Hitting this limit triggers the engine control unit to cut fuel or spark to protect the valvetrain from floating or the connecting rods from snapping.
Heard on the job
I had to redline it in second gear just to merge onto the highway with that heavy trailer.
Insider tip
Newer fuel-injected cars have electronic limiters that bounce the RPM safely at the redline, but older carbureted engines will keep spinning until they destroy themselves.
Also heard as
- max out