What Does “Cold” Mean To An Engine?

Your engine is far more sensitive to cold ambient conditions than you might think.


What Is “Cold”?

The answer depends on your physiology and environment. For us northerners who expect six-month winters, the word “cold” doesn’t enter our vocabulary until the temperature drops below zero. And, even in the midst of a brutal cold snap, a day of sunshine and -10°F (-23°C) temps can feel comfortable after wind chills of -50°F (-46°C) or colder.

Head down south and the definition of “cold” changes. A 60°F (16°C) day can feel cold after months of triple-digit summer temperatures. Of course, some people are more susceptible to cold than others. Without fail, every time we have a snowstorm around here, you’ll see a guy at the gas station or grocery store in shorts and flip-flops right next to someone wrapped in a winter coat and scarf.

The definition of “cold” is different for each person. It’s also different for your engine.

Cold-Flow Matters To All Drivers

We often tout the excellent cold-flow properties of AMSOIL synthetic lubricants on these pages and in our marketing material. Drivers down south may be tempted to ignore that benefit, but it applies in those environments, too.

While true that oil thickens more in winter weather and causes increased starting difficulty, an engine is considered “cold” after it’s sat long enough to cool to ambient temperature, typically overnight. As it cools, oil viscosity increases (it thickens). When it’s time to start your vehicle in the morning, the thicker oil doesn’t flow through the engine as readily as it does when it’s at operating temperature. Cold, thick oil can be slow to flow through the tiny oil passages throughout your engine, like those in the camshaft shown here. It’s during this time that vital engine parts can operate without lubrication, increasing wear.

Camshaft Showing Small Oil Ports

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

Lower Pour Points = Better Protection

An oil’s pour point reflects how well it flows at low temperatures and how well it protects against cold-start wear. This is vital considering most wear occurs at startup.

Pour point is defined as the lowest temperature at which a motor oil will continue to flow under prescribed conditions. The Pour Point Test (ASTM D97) spells out the standard procedure for determining an oil’s pour point

The sample is slowly cooled and tilted sideways every time the temperature drops 5°F (3°C). The pour point is the lowest temperature at which the oil still flows. Oils with lower pour points flow more readily at startup, providing critical lubrication faster for reduced wear and maximum engine life. Whether you’re in northern Wisconsin in February or Arizona in August, this is important if you want to protect your engine.

AMSOIL offers better startup lubrication

AMSOIL synthetic lubricants provide better cold-flow properties than conventional oils and most other synthetic oils. Our synthetic base oils don’t contain the waxes inherent to conventional oils. As a result, they provide increased fluidity during cold starts. This translates into oil that flows almost immediately through your engine, protecting it against wear. That’s a great selling point no matter how you define “cold.”

Reproduced With The Permission Of AMSOIL INC. All Rights Reserved.

SLS Note: When ASTM tests to determine the oils viscosity (ASTM D445), the test at 100℃ (212°F), is roughly considered the engines normal operating temperature while 40℃ (104°F) is the “Cold” oil temperature. As Mr. Erickson stated above, “The definition of “cold” is different for each person. It’s also different for your engine.” Very few if any of us would consider a temperature of 104°F to be “Cold” yet, for engine oil, it is.

If you have ever had to add oil stored in a cold garage or shed to your vehicle, you know how slow the oil can pour. If not, and you feel like doing a little experiment, take a clear bottle of cooking oil and put it in the refrigerator overnight. This oil which pours easily at 70°F is much thicker and slower pouring at 40°F and might be solid (below its pour point) if left in the freezer overnight. Now think of trying to pump that cold oil through your oil filter and spaces smaller than a hair in your engine and you can see why a low pour point (and quality synthetic lubricants) are important for the life of your engine.

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