Superior Cold-Start Engine Protection

Most engine wear occurs at startup. That’s primarily because oils thicken as the temperature drops. Cold oil doesn’t flow as fast and, in some cases, may not be able to flow through tiny oil passages at all. When that happens, engine components are forced to operate without lubrication until the engine warms up the oil enough for it to flow, greatly accelerating wear. For those reasons, cold-flow capability is a critical measure of motor oil performance.

How well does AMSOIL Signature Series 100% Synthetic Motor Oil flow in the cold? Its data sheet answers that. Pour point is the lowest temperature at which an oil still flows. Across the Signature Series lineup, typical pour points range from -48°C (-54°F) to -54°C (-65°F).

The 0W-20 has a typical pour point of -54°C (-65°F) and the 5W-30 -48°C (-54°F). Oil that keeps flowing in extreme cold reaches critical engine parts sooner at startup, when most wear occurs.

Causes of startup engine wear

The exact percentage of engine wear that occurs at startup depends on a mix of several factors. The factors below accelerate wear:

• Motor oil doesn’t flow, temporarily starving the engine of oil.
• Gravity causes much of the oil to flow into the oil sump, leaving components unprotected.
• Condensation forms inside the engine that causes rust and corrosion.
• Richer air/fuel mixture at startup washes oil from the cylinder walls.
• Cold piston rings and cylinders don’t seal as well, allowing combustion gases to “blow by” the rings and contaminate the oil.

While all these factors are important, lack of oil due to poor cold-flow properties is the biggest culprit.

Conventional oils perform worse

The difference between AMSOIL and conventional motor oils at startup is even more stark. Conventional lubricants contain paraffins, or waxes, that solidify when the temperature drops. These waxes cause the oil to thicken to a point where they barely flow at frigid temps.

We cooled a conventional oil and AMSOIL Signature Series 5W-30 Synthetic Motor Oil to -40ºC. The conventional oil thickened so much it barely flowed from the beaker. Check out the video below to see for yourself.

Impacts of poor cold flow

Thick oil can prevent the crankshaft from spinning fast enough to start the engine, leaving you stranded.

In addition, thick oil can fail to flow through the screen openings on the oil pickup tube, starving the engine of oil for several vital moments.

Oil may also fail to flow through the tiny passages in the crankshaft to lubricate the main bearings. Similar passages in the camshaft ensure the engine’s upper end is lubricated. The further away from the oil pump these passages are, the longer it takes oil to reach components at startup.

Poor cold-flow properties can also affect variable valve timing (VVT) systems. Engines equipped with VVT have solenoids with tiny openings (about the thickness of two sheets of paper) through which the oil flows and acts as a hydraulic fluid to actuate VVT components. Oil that fails to flow through these tiny passages reduces VVT performance and can trigger a check-engine light.

Warm places, cold starts

What exactly is a cold-start? It’s true that oil thickens more in sub-zero winter weather. Therefore, cold-start wear is a greater threat in cold climates, particularly if you’re using conventional motor oil. However, it doesn’t have to be anywhere near -20°F (-29°C) to be considered a “cold-start.”

An engine is considered “cold” after it’s sat long enough to cool to ambient temperature, typically overnight. When it’s time to start your vehicle in the morning, the thicker oil doesn’t flow as rapidly as it does at operating temperature, leaving components vulnerable for a short time. Therefore, even in warmer climates, the motor oil’s cold-start capability matters for vehicle longevity.

Protect your engine

Since most engine wear happens at startup, taking care of your engine should include using a motor oil with outstanding cold-flow capabilities. As independent third-party testing reveals, Signature Series offers superior protection for cold starts – and less engine wear at startup.

^PPBased on independent third-party testing in the industry-standard ASTM D5293 Cold Crank Simulator test as required by SAE J300.

This article is part of our Battery and Cooling System Care guide. See every article in the guide.

Related Reading

• 5W-20 vs. 5W-30 vs. 10W-30: What’s the Difference?
• All You Need to Know About Oil Cold Flow