Your engine moves before oil pressure is fully established.
Why the first seconds of every startup are a vulnerable moment.
What happens at startup.
After shutdown, oil can drain away from parts of the lubrication circuit. At the next startup, the crankshaft, camshaft and other moving components begin operating while pressure is building. Oil films and residual lubrication still provide some protection, but startup can involve mixed or boundary lubrication—conditions that may increase wear.
- Oil collects in the sump after shutdown
- Critical components need lubrication during startup
Concept illustrationA schematic of an oil circuit, not an engine drawing; real oil paths vary by engine.
A pre-prime pump can create pressure in a lubrication circuit. But the link between static pre-pressurization, a hydrodynamic bearing film and measured wear reduction depends on engine motion and operating conditions, and pressure alone does not fully separate stationary crankshaft journals. That is why the test program matters.
What “dry start” really means.
Why does startup matter?
After shutdown, some oil drains from engine passages. At startup, lubrication pressure must be re-established. Certain components can experience mixed or boundary lubrication during that transition.
Does an engine start completely dry?
Not necessarily. Residual oil films usually remain, and some engines retain oil in galleries. “Dry start” is shorthand for the period before normal oil pressure and circulation are established.
Oil pressure first. Engine startup second.
The way engines start has remained largely unchanged. We are working to change what happens before they turn.