is located on the side or bottom of the engine block and oil filters are key components in safeguarding a vehicle's engine. How does this device (that dates back since the 1920's) work? As an oil pump circulates the oil through the engine, it circulates engine oil as it passes through the oil filter. Then the oil filter goes to work by protecting the engine by blocking large particles that might cause harm to the engine if left unchecked and allowed to circulate freely.