Engineering
Tribology of Journal Bearings Under Transient Start-Stop Conditions
Quick fact
A journal bearing can experience more wear during a single engine start than during hours of steady highway driving, because the protective oil film is squeezed out before the shaft reaches hydrodynamic speed.
Why this is interesting
Your car's engine automatically shuts off at every red light to save fuel. But each restart may be wearing out its most critical bearings—a hidden cost of stop-start technology.