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How Does an Oil Pump Work?

Engine oil pump

Wondering how an oil pump contributes to the overall health and operation of your vehicle’s engine? The short version has to do with the need to maintain steady oil pressure inside your motor in order to keep lubricant flowing to each and every component, crevice and channel built into the unit. To do this, an oil pump that is capable of generating the right psi, or pounds per square inch of oil pressure is required. Think of it as the heart of your engine ensuring that lubricant never stops flowing.

How does it get the job done? Let’s break it down.

Oil Pressure Isn’t Constant

If you’ve ever driven a car with an accurate oil pump gauge that tracks actual pressure, you’ll notice that the amount of pressure in the engine doesn’t stay constant. That’s not a design flaw — an idling engine doesn’t require as much pressure to keep all of its moving parts lubricated as one that’s running at a much higher rate of speed. Typically, every 1,000 rpm needs 10 psi of pressure, although that figure can vary with high-performance engines.

The direct correlation between oil pressure and engine speed is related to the oil pump design itself. The devices are linked to the engine’s crankshaft in order to get the drive they need to function, usually operating at half crank speed. The amount of pressure produced is a function of the engine speed itself.

Each Design Is Different
Engine oil pump

Most engines run a wet sump oiling system, which means that the bottom of the engine’s rotating components pass through the oil pan and throw lubricant up onto the cylinders as it spins. The oil pump is asked to push oil to the top of the motor.

There are many pump designs, but each centers around the concept of a set of gears or rotors pressurizing oil by forcing it against the housing where the rotation of the gears or rotor takes place. Gear pumps are an older design, while rotors — particularly eccentric rotor designs, which consist of two rotors featuring more lobes on one side than the other — are more common in modern vehicles. There are also designs that use sliding vanes on a rotor, as well as dry sump oiling systems that eliminate the oil pan entirely and rely on a pair of oil pumps to keep the entire rotating assembly lubricated.

Each type of pump pushes oil through the engine’s oil filter, then up through the motor to the top, where it eventually drips back down again into the oil pan. There are also pressure valves that open to make sure that oil doesn’t go above a certain psi that could damage internal components.

In short, there are different pump designs in modern vehicles, but it’s a necessary component to make your car’s engine function properly.

Check out all the engine parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your engine’s oil pump, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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