Engine Sludge Is Easily Avoidable

John Baker & Associates |Jul 24, 2019 4:20 PM

Engine sludge.

It’s a back gelatinous substance that wreaks havoc in engines. And long before the engine’s demise, engine sludge can foul engine sensors and interfere with performance. Some mechanics call it the “black death.”

How does motor oil, which is fluid, become a semi-solid paste or gel inside an engine?

Here’s what we’ll cover:

How engine sludge forms
The effects of engine sludge
Synthetic oil helps prevent engine sludge
High-quality additives fight engine sludge
Severe service invites engine sludge

How engine sludge forms

Engine sludge is the result of a series of chemical reactions.

The lubricant degrades as it is exposed to oxygen and elevated temperatures. The higher the temperature, the more rapid the rate of degradation. In fact, every 18°F (10°C) increase in temperature doubles the rate of oxidation.
Many people still believe any oil is fine as long as you change it often but 95% of the brands out there do not address that inch of protection when you really need it!! We’ve all had issues where the engine is overheating or some situation where adequate lubrication isn’t available. AMSOIL offers 75% more protection when you need it and our diesel oils offer 6X more protection than required by industry testing.

The by-products of this reaction form highly reactive compounds that further degrade the lubricant. Their by-products react with other contaminants, forming organic acids and high-molecular-weight polymeric products. These products further react, forming the insoluble product known more commonly as sludge.

What begins as a thin film of lacquer or varnish deposits on hot or cold metal surfaces and bakes into an expensive mess.

The effects of engine sludge

Sludge can block the oil passages and oil-pump pick-up screen, resulting in oil starvation. Often, the negative effects are cumulative rather than sudden.

Many engines with variable valve timing (VVT) use oil-pressure-operated mechanical devices to change valve timing, duration and lift. Sludge can plug the solenoid screen or oil gallies and impact the operation of VVT mechanisms, eventually leading to a costly repair bill. Sludge reduces efficiency and increases time and money spent on maintenance.

Who doesn’t want a cooler engine? Sludge, even the early stages prevents the engine from dispersing heat efficiently. Why would you risk a Group III “synthetic” which does leave deposits adding to or resulting into an engine which struggles to exhaust heat.

Synthetic oil helps prevent engine sludge

Fortunately, sludge and varnish deposits are something oil manufacturers can control. Using thermally stable synthetic base oils reduces the rate of degradation (oxidation). (Yes – and that is “Real 100%” Synthetics – not the ones they currently call “Fully”..

Anti-oxidant additives help reduce the rate of degradation as well. One of the most widely used is zinc dithiophosphate. Not only is it an excellent oxidation inhibitor, it is an outstanding anti-wear additive as well.

High-quality additives fight engine sludge

We can further address many of the issues occurring after the initial oxidation stage.

Additives, such as detergents and dispersants, are commonly part of motor oil formulation. They help promote the suspension of contaminants within the oil and keep them from agglomerating.

Detergents, which are also alkaline in nature, assist in neutralizing acids generated in the sludge-building process. Anti-oxidant, dispersant and detergent additives are consumed during use.

To achieve maximum life expectancy, use an oil with high concentrations of anti-oxidant, dispersant and detergent additives.

AMSOIL Signature Series Synthetic Motor Oil, for example, has 50 percent more detergents* to help keep oil passages clean and promote oil circulation. It provides 90 percent better protection against sludge**.

Signature Series Synthetic Motor Oil was subjected to the Sequence VG test to measure its ability to prevent sludge. Signature Series produced an oil pick-up tube screen virtually free from sludge. Our unique combination of detergents and high-quality base oils control oxidation and sludge to keep engines clean and efficient.

PDF of the test where AMSOIL has this done (Southwest Research)

Buy Signature Series

Severe service invites engine sludge

Equipment operating conditions also influence the likelihood of sludge or varnish issues.

Stop-and-go driving, frequent/long-term idling and operation in excessively hot or cold weather can increase the likelihood of sludge and varnish, especially if using more volatile conventional oils. If sludge has already formed, you can use an engine flush to clean sludge from your engine.

Interestingly, most auto manufacturers note in their owner’s manual that operation under any of the above conditions is considered severe service and requires more frequent oil changes.

From a mechanical standpoint, things like adding too much oil to the oil sump, antifreeze contamination, excessive soot loading, excessive oil foaming, poor engine-combustion efficiency, excessive blow-by and emission-control-system issues can all lead to the formation of sludge and varnish.

By practicing good maintenance and using properly formulated, premium synthetic lubricants, like AMSOIL synthetic motor oil, your vehicle won’t succumb to the “black death.”

Taking it a step further which many of our customers do – to make sure your vehicle is always running in peak condition one thing is to have your oil analyzed. I do it not so much to see how the oil is doing but to measure what may be going on in the engine to deplete detergents or to test for any out of typical wear levels, fuel in the crankcase, and to see if the viscosity is still on par. Oil analysis kits are easy to use especially when you have the dipstick extraction pump.

*vs. AMSOIL OE Motor Oil
**Based on independent testing of AMSOIL Signature Series 5W-30 in the ASTM D6593 engine test for oil screen plugging as required by the API SN PLUS specification.

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.

Tag: VVT

How Engine Sludge Forms. And How To Prevent It.