Skip to main content

Where Oil Goes and What it Does

Written by Charleen

The Responsibilities of Your Motor Oil

A typical engine contains hundreds of parts, none of which could function properly without oil. Far from a simple commodity, oil is a dynamic enabler of performance. It must lubricate, cool, protect, seal, actuate components and more. And it must do it all while exposed to tremendous heat and stress. Here, we highlight key areas where oil goes inside your engine and what it does once it’s there.

Variable Valve Timing (VVT)

To increase fuel economy and reduce emissions, most modern engines use VVT systems to adjust when the valves open and close. VVT systems use motor oil as a hydraulic fluid to actuate cam-phaser components. Solenoids, like the one shown here, control cam-phaser timing. These solenoids contain tiny openings through which the oil must flow. Even minimal varnish or deposits can disrupt the system, triggering a check-engine light. The oil must maintain viscosity to function as a hydraulic fluid while resisting deposits to maximize VVT system performance.

Valves and Seals

Valve seals prevent oil from running down the valve stems. This keeps the oil on valvetrain components and prevents it from entering the intake and exhaust ports and burning, increasing oil consumption. The oil must condition these seals to prevent drying, cracking and leaking. The oil also helps cool the valves and control cylinder-head deposits, helping prevent valve sticking.

Main Seals

The seals at the ends of the crankshaft keep the oil inside the engine. The oil must condition seals to prevent drying, cracking and leaking.

Wrist Pins & Undercrowns

Crankshaft eccentrics splash-lubricate the cylinders, wrist pins and piston undercrowns. Some engines have small nozzles that spray oil directly onto the wrist pins and undercrowns. The rapidly spinning crankshaft causes air entrainment in the oil, creating foam. If foam bubbles in the oil pass between metal parts, they collapse and cause metal-to-metal contact. The oil must contain anti-foam additives to quickly dissipate foam. The oil must also contain detergent additives to help keep the wrist pins and undercrowns clean.

Connecting Rods & Main Bearings

Combustion drives the pistons down the cylinder, creating intense pressure between the connecting rods, main journals and bearings. Oil molecules act like microscopic ball bearings that support this pressure and allow the rods and crankshaft to rotate without metal-to-metal contact. The oil must maintain its protective viscosity despite increased pressures, temperatures and shearing forces. If the fluid film weakens, the oil will squeeze from between the journal and bearing clearances, resulting in metal-to-metal contact and bearing wear.

Camshaft

The camshaft and lifters open and close the intake and exhaust valves. To prevent wear, the oil must form a strong fluid film that separates the cam lobes and lifters. It also must contain robust anti-wear additives to maximize the life of the camshaft and bearings. As the image below shows, AMSOIL Signature Series 0W-20 Synthetic Motor Oil did an excellent job protecting against cam wear in rigorous, third-party testing.

Pistons, Rings & Cylinders

The pistons compress the air in preparation for combustion. The piston rings perform several critical functions: they must seal the combustion chamber, return excess oil on the cylinder walls to the sump and transfer extreme piston-crown heat to the cylinder walls.

To prevent wear despite intense heat and shearing forces, oil must maintain a strong, consistent film between the rings and cylinder walls. It also must prevent deposits that cause ring sticking, increased oil consumption, compression changes and low-speed pre-ignition (LSPI).

Signature Series Synthetic Motor Oil achieved 100 percent protection against LSPI1 in the engine test required by the GM* dexos1® Gen 2 specification – zero occurrences were recorded throughout five consecutive tests.

Oil Galleries & Passages

An engine contains an intricate network of oil galleries and passages that carry oil to components. Passages in the crankshaft, for example, carry pressurized oil to the rod and main bearings, while similar passages in the upper end carry oil to the valvetrain. Oil that thickens in the cold can fail to flow through narrow passages and starve the engine of oil. Sludge, meanwhile, can plug passages and have the same effect. The oil must remain fluid when the temperature drops, and it must prevent sludge.

Oil Pick-Up Tube Screen

The oil pump draws oil through a fine screen and pressurizes it so it can flow through the oil galleries and passages to the bearings and valvetrain. Sludge can plug the screen, starving the engine of oil. Oil that thickens too much to pass through the screen has the same effect. Therefore, oil must remain fluid when cold to pass through the screen and flow throughout the engine at startup (when most wear occurs). The oil also must prevent sludge to keep galleries and passages clean, ensuring maximum oil flow.

Knowledge Base, , , , , , , , , , , , , ,

How do we define “severe service”?

Written by Charleen

How do we define “severe service”?

When pushing our lubricants to their limits, we sometimes find the limits of the test equipment first.

Matt Erickson | TECHNICAL MANAGER – PCLT PRODUCTS AND MECHANICAL R&D

One of my responsibilities here at AMSOIL is to help develop tests in our mechanical lab designed to push lubricants to their limits, both ours and those of our competitors. An effective performance test accelerates lubricant degradation and forces the oil to its breaking point sooner than if tested in the field. This provides more data, faster.

The definition of “severe”

Given the severity of our testing, what happens when the equipment we test fails before our lubricants? Honestly, it causes us to simultaneously rejoice and curse. On one hand, we know our products withstand the toughest conditions we throw at them. On the other, we have to contend with the extra cost and hassle of test equipment that just isn’t built to handle the punishing conditions.

The August 2016 Tech Talk revealed how some two- and four-stroke equipment we’ve tested couldn’t stand up to our test conditions. We’ve run into the same predicament in the passenger car/light-truck market, too.

One recent incident involved the popular General Motors* 3.8L motor. Historically, the GM 3.8L is a rocksolid engine that’s powered millions of cars over the years. It’s a fixture in industry performance testing. One standardized test uses this engine under severe conditions for 100 hours. But our oils soldier through that test like a walk in the park, so we have to triple its length to 300 hours to get useful data. Not an easy task for equipment not designed to handle such extremes.

Well, we recently blew up a GM 3.8L engine. The image shows some of the carnage we found after removing the oil pan. All those bits and pieces used to be a piston.

We ran this test under extreme conditions, as if you were towing continuously at highway speeds uphill for weeks.

Unleaded gasoline

What happened, you ask? First, I’ll ease any concerns you might have: it wasn’t the oil’s fault. We were in uncharted territory, never having an oil last so long in this test before, so we knew we were on borrowed time. In fact, after more than four weeks of testing, the oil hadn’t even reached its breaking point. One of the exhaust valves broke off and fell into the cylinder, where it and the piston were pulverized into the mess you see here. As the piston and valve debris made its way to the oil pan, the crankshaft caught it and blew a hole in the side of the engine block. The severity of our test conditions combined with valve seat recession are to blame.

Years ago, lead was added to gasoline to, among other functions, lubricate the valve seats. Once lead was officially banned from gasoline, in 1996, the fuel no longer provided the same level of valve-seat protection. This lack of protection, combined with the extreme conditions of our test, invited valve recession. When valve seats recede, the valve no longer seats evenly. The result is a loss of heat-transfer that overheats and erodes the valve, as well as an uneven side load that causes the valve to bend slightly on every cycle. This onetwo punch eventually caused the valve to fail. We ran this test under extreme conditions, as if you were towing continuously at highway speeds uphill for weeks. Oil temperatures exceeded 300ºF. The extreme, 1,500ºF exhaust gas temperatures, combined with the constant stress of unevenly eroded valve seats, eventually led to valve failure, snapping a valve in half and destroying the engine.

But our oils soldier through that test like a walk in the park, so we have to triple its length to 300 hours to get useful data. Not an easy task for equipment not designed to handle such extremes.

Suitable for continued use

The good news, however, is the motor oil was still good. Even after hundreds of hours of operation so severe it destroyed the engine, the oil analysis still looked great. It made me smile to see our oil last that long, but it also made me cringe because we were going to have to once again re-test to try to get the oil to break.

This conundrum might present challenges to us engineers, but it amounts to you and your customers receiving the best synthetic lubricants available. We’re happy to keep blowing up engines in our mechanical lab to ensure your engines are protected out in the field.

Given the severe nature of our performance tests, the test equipment sometimes fails before our lubricants.

Tech Articles, , , , , , , , , , , , , , ,