Q: We have repaired a BMW 320 sedan. The car consumes 0.2L of oil for 100km, which means 1L of oil for every 500km. After replacing the exhaust valve, the oil burning is still serious. How can I diagnose whether it is caused by the valve seal or the piston ring?
A: If the exhaust pipe emits blue and white smoke for a while when starting or accelerating for the first time every day, or if the hot car idles for a while and also emits blue and white smoke when accelerating, it can be diagnosed that it is a problem with the valve seal. If the exhaust gas is heavy or blue and white smoke is emitted after the oil cap is opened after the car is heated, it can be diagnosed that the oil burning is caused by the wear of the piston ring.