* Metal-on-metal contact: Engine components (crankshaft, connecting rods, camshaft, bearings, etc.) will grind against each other without the oil film to separate them. This generates immense friction and heat.
* Scuffing and scoring: The surfaces of the metal parts will become damaged, creating deep scratches and gouges.
* Seizure: The engine will seize up, meaning the moving parts become locked together, rendering it completely immobile. It will not turn over.
* Bearing failure: The bearings, which allow for smooth rotation, will be destroyed.
* Internal damage: Beyond bearing failure, the connecting rods can bend or break, the crankshaft can fracture, and other internal components can be severely damaged.
In short, running an engine without oil results in a completely destroyed engine that will require a replacement, not just a repair. A lack of oil pressure will usually trigger warning lights in a vehicle well before a catastrophic failure, however.
