HOW TO CHECK ENGINE WEAR BEFORE BUYING A CAR

How to perform a blow-by test

Start by removing the oil cap and observing any movement while the engine is running. Excessive blow-by gases may indicate worn piston rings and poor compression. When the PCV (positive crankcase ventilation) is disconnected, blow-by gases are not recirculated back into the combustion chambers and instead escape through the oil cap. If the cap moves excessively or even flies off, it suggests the engine is significantly worn out.