2002 Toyota Avalon Owners Manual - Page 210

'02 AVALON U (L/O 0107) Facts about engine oil consumption D Keep the trunk lid closed while driving. An open or unsealed trunk lid may cause exhaust gases to be drawn into the vehicle. FUNCTIONS OF ENGINE OIL Engine oil has the primary functions of lubricating and cooling the inside of the engine, and plays a major role in maintaining the engine in proper working order. ENGINE OIL CONSUMPTION It is normal that an engine should consume some engine oil during normal engine operation. The causes of oil consumption in a normal engine are as follows. D Oil is also used to lubricate the stems of the intake valves. Some of this oil is sucked into the combustion chamber together with the intake air and is burned along with the fuel. High temperature exhaust gases also burn the oil used to lubricate the exhaust valve stems. The amount of engine oil consumed depends on the viscosity of the oil, the quality of the oil and the conditions the vehicle is driven under. More oil is consumed by high−speed driving and frequent acceleration and deceleration. A new engine consumes more oil, since its pistons, piston rings and cylinder walls have not become conditioned. When judging the amount of oil consumption, note the that oil may become diluted and make it difficult to judge the true level accurately. As an example, if a vehicle is used for repeated short trips, and consumes a normal amount of oil, the dipstick may not show any drop in the oil level at all, even after 1000 km (600 miles) or more. This is because the oil is gradually becoming diluted with fuel or moisture, making it appear that the oil level has not changed. D To allow proper operation of your vehicle's ventilation system, keep the inlet grilles in front of the windshield clear of snow, leaves, or other obstructions. D If you smell exhaust fumes in the vehicle, drive with the windows open and the trunk lid closed. Have the cause immediately located and corrected. D Oil is used to lubricate pistons, piston rings and cylinders. A thin film of oil is left on the cylinder wall when a piston moves downwards in the cylinder. High negative pressure generated when the vehicle is decelerating sucks some of this oil into the combustion chamber. This oil as well as some part of the oil film left on the cylinder wall is burned by the high temperature combustion gases during the combustion process. 2002 MY AVALON_U (OM22493U) 209