Vehicle emission control systems can markedly affect the environment within the engine crankcase, and could thereby increase engine deposits, wear, and oil degradation. Tests run using 1965-1970 model United States passenger cars, operating with leaded commercial gasolines in several types of service, evaluated the effects on deposits and wear of three types of experimental vehicle emission control systems:
- 1.
Crankcase storage systems for reducing vehicle evaporative emissions.
- 2.
An exhaust gas recirculation (EGR) system for reducing oxides of nitrogen.
- 3.
Positive crankcase ventilation (PCV) systems for controlling crankcase emissions.
In engines operated with production crankcase purging rates, crankcase storage increased engine rusting in short-trip service, and increased sludging and valve train wear in low-speed, stop-and-go service. Reducing the crankcase purging rate to overcome hot-starting and driveability problems with crankcase storage caused even larger deposit and wear increases.
Engine rusting in short-trip service was increased with EGR. In other tests, heavy lead-salt deposits accumulated in the recirculation system.
Doubling the PCV valve idle air-flow rate greatly reduced engine rusting in short-trip service, and reduced engine deposits and oil oxidation in mixed city-suburban-expressway service.