![]() A roller/needle bearing-equipped auto engine would have higher power and longer life, but at what production cost? I have flown model airplanes for 40 years and many of my highest-revving engines (25,000+ rpm compared to 2,500 rpm in an automobile engine) are equipped with roller bearings for lower friction and higher rpm. Generally they turn at lower rpm (speed) than gasoline car motors. Many larger engines have needle/roller bearings. I know it would cost a fortune to build such a motor, but it would last forever. Looking aside for a minute, I would like to see an automotive engine with roller or needle bearings replace the far cheaper and sufficiently long-lived sleeve bearings. ![]() A flickering oil light or a slight tapping sound in the rocker arm area on the topside of the motor is a good indication that not enough oil under pressure is reaching the top end of the engine. If the clearance is too much, say 0.004 of an inch or better, pressure starts falling in the upper end of the engine. It is important to note that some of the oil is forced out of the sides of the bearings and drips back into the sump. Metal should never touch other metallic surfaces while it is moving. Under pressure and within the correct operating temperature, the oil protects and prolongs the life of the machined parts. This thin space, usually one-thousandth of an inch on newer engines, holds a thin film of oil between the bearings and the moving surfaces on the crankshaft. The block has main bearings on the crankshaft, and connecting rods bearings are on the crank throws. The bearings are simple metal sleeves encircling the rotating components of the engine. Oil is forced into the space between the bearings making contact with the crankshaft journals and the journals. The first and most important job of motor oil is to lubricate the rotating components of an engine, and it must be under a good pressure to do its job. The oil filter also has a bypass valve to keep the pressure from dropping too low if the filter becomes clogged. ![]() 2 Any pressure higher than this will be vented back to the sump because high oil pressure can damage bearings.įrom the pump, it goes to the outside of the oil filter, and there it is forced through the filter media to the center, where it exits into the oil galleries inside the engine. The valve allows the oil to leave only under a specified pressure, usually between 1 and 60 lbs./in. Many people do not realize that most oil pumps are just a set of special gears, which take in the oil under low pressure and squeeze the oil to a high pressure, where it then passes through a chamber with a spring-loaded valve. The screen prevents large pieces of trash, usually lrger than 1/32nd of an inch, from entering the oil pump. The tube and screen are submerged in the oil at a depth of about four inches. The screen is attached to a pickup tube, which leads directly to the oil pump. The oil goes through several different paths returning to the bottom - but only one path, under pressure, to do its job.įigure 1 shows a tube with a loose-weave metal screen at the bottom of the pan. Where does the oil travel, in what order, and what exactly does it do inside your engine?įirst, the oil you pour in the top of the engine goes through many paths eventually arriving in the bottom oil pan, often called the sump, where the drain plug is located. The answer to these questions will determine the best oil for your vehicle, and how well it protects and lubricates your engine while it goes around and around inside. To answer that question, I would use the Socratic method and ask a few questions of my own: What kind of car do you drive? What driving conditions do you encounter most? Where do you live? How old is your car? “How often should I change my car’s oil, and what should I use?” One of the most common questions I get is: But I am surprised at the number of people who do not have a true picture of the path the oil travels while it makes its way around inside of the engine. Because I have worked in auto repair for 35 years, it is no mystery to me what happens between filling and changing the oil. Most people know to add oil to the top of their engines, and that oil drains out the bottom.
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