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What Motor Oil is Best for Winter? (And Other Cold-Weather Questions)

The Best Winter Motor and Transmission Oil Choice

Synthetic oil is best for winter.

We’re done here.

If only it were that simple. But most people want empirical data to support such claims.

Well, take a look at the video. We cooled a conventional 5W-30 motor oil and AMSOIL Signature Series 5W-30 Synthetic Motor Oil to -40º. As you can see, the conventional oil thickened so much that it barely flowed from the beaker. The AMSOIL product, on the other hand, flows almost immediately.

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Why the dramatic performance difference? In answering that question, I’ll also answer the question hoss61761 poses on social media:

Conventional oils contain waxes that solidify when the temperature drops. This severely impairs the oil’s ability to flow when you crank your engine. In some cases, the oil can thicken so much that it prevents the crankshaft from spinning fast enough to start the engine.

Prior to using AMSOIL, I had a Cutlass Ciera that was notorious for refusing to start on our cold Minnesota mornings. The dirt-cheap big-box-retailer oil I used back then thickened so much the engine would barely turn over.

Why synthetics flow better in winter weather

Synthetics, in contrast, don’t contain waxes due to the chemical-reaction process used to construct synthetic base oils. As a result, synthetics demonstrate far better cold-flow properties than conventional oil. Not only will your vehicle start more easily (I’ve yet to have one of my vehicles using AMSOIL fail to start, even with temps pushing -30ºF), the oil will flow more quickly, ensuring oil reaches vital components faster. This, in turn, maximizes wear protection, helping your engine last longer.

Check the oil’s pour point

If you want more data to prove synthetics’ cold-weather superiority, check the oil’s Product Data Sheet. Look for the oil’s pour point. Lower numbers indicate better cold-flow, thus better cold-weather performance.

In the example here, you can see that AMSOIL Signature Series 5W-30, the same oil shown in the video above, has a pour point of -58ºF (-50ºC).

What is cold?

Not to get existential here, but it’s a relevant question. Folks in the south whose idea of winter is putting shoes on for a couple weeks in January may think they’re off the hook. Do they need to waste mental energy on motor oil cold-flow properties?

Good cold-flow is important to Southerners, too. Here’s why.

Engineers agree that most engine wear occurs during cold starts. There are several reasons, but two concern us for this discussion:

  • Gravity causes much of the oil to fall back into the oil sump, leaving components unprotected
  • Cold oil doesn’t flow immediately at startup, temporarily starving the engine of oil

While true that oil thickens more in sub-zero 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.

The oil inside your engine cools as it sits overnight. As it cools, its 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. It’s during this time that vital engine parts can operate without lubrication, increasing wear. So, even in warm climates, cold-start wear is a problem. Southerners are well-advised to use a good synthetic oil with excellent cold-flow properties, too.

Thick or thin oil in winter?

Motorists sometimes ask if they should use thicker or thinner oil in the winter. Fortunately for them, we wrote a whole post on that topic. Check it out here.

Should I Switch to a Lighter Viscosity Oil in Winter?

To summarize, use the lowest viscosity oil your vehicle manufacturer recommends in the winter. Most automakers recommend a lone viscosity year-round. But some allow you to switch to a lower viscosity in winter, which helps improve cold-flow.

If your owner’s manual says you can switch to a lower viscosity oil in winter, go for it.

Shift to better winter protection

While I have you here, I should talk about transmission fluid, too. Like motor oil, it thickens in cold weather. The cold, thick fluid doesn’t flow readily through the intricate network of passageways in the transmission valve body or through the small solenoid openings. What does that mean to you?

  • Delayed shifts
  • Elongated shifts
  • Hard/harsh shifts
  • Reduced wear protection

Cold, thick transmission fluid doesn’t flow readily through narrow valve-body passages, leading to poor shift quality.

Again, I’ll go to the well of personal experience. After buying a Honda CR-V several years ago, I switched to AMSOIL synthetic motor oil…but I neglected to change the transmission fluid. Fast-forward to winter and one of our trademark -20ºF mornings with a wind chill pushing past -40º. The Honda started, but she shifted slowly and with much wailing and gnashing of teeth. The entire vehicle shuddered as it reluctantly found second gear heading down the road.

Switching to synthetic transmission fluid solved the problem. The fluid flows much more readily in the cold, which translates into smoother shifts. It also means the gears and bearing are receiving vital lubrication, too. Anyone who’s shelled out thousands of dollars for a tranny replacement knows how important that is.

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Bottom Line: Synthetic motor oil and drivetrain lubricants perform better in the cold than conventional oils. They flow better for easier starts, smoother shifts and better protection against wear. Upgrade to synthetics to maximize cold-weather protection and performance.

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Watch Scott Judnick Go Big – And Why We’re Into Snow

Watch Scott Judnick Go Big – And Why We’re Into Snow

At AMSOIL, we like to do things big. And when it comes to the world of Snocross, Scott Judnick of Judnick Motorsports likes to do things just as big. Check out his story below.

It’s About the People

Twenty-two years ago, Scott Judnick took his sons racing. Within just a few years he was running a rig across the country to race. His two sons developed into professional riders complete with mechanics and trailers set-up for the AMSOIL Championship Snocross Series. Find Judnick anywhere on the track or in the pits and you are sure to be greeted with a smile and a “How are ya?”

For Judnick, it’s all about the people within the racing community. Fielding the dreams of the three young racers on his team is just a bonus.

Overcoming Adversity

Judnick went into the 2018-19 Snocross season with notable riders expected to dominate the Pro, Pro Lite and Sport classes. The season started on a high note with Sport rider Carson Alread taking the checkers to open the season in Duluth, Minn.

Noticeably absent from the Friday night DOMINATOR race was Pro Lite rider Nick Lorenz. A re-aggravated knee injury forced Lorenz to take it easy opening weekend. After further observation, he underwent surgery that ended his season before it started. Making matters worse for the team, a scary landing during practice in Canterbury, Minn., left Alread sidelined for the remainder of the season, too.

But that didn’t stop Judnick from continuing to compete. He signed Canadian standout RJ Roy, along with Pro rider Corin Todd. Roy has proven he can hang with the big boys, landing just short of the podium multiple rounds.

AMSOIL Products Keep Sleds Running Strong

Race sleds operate in extreme conditions. Judnick relies on AMSOIL DOMINATOR Synthetic 2-Stroke Racing Oil to keep his race sleds running in those extreme conditions.

“Our engines are tuned to run on the very edge and placed under extreme demands in extreme weather conditions,” said Judnick. “We’ve been using DOMINATOR since its inception and it has never let us down.”

DOMINATOR® Synthetic 2-Stroke Racing Oil

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Not to be forgotten, the chaincases on these sleds also need attention. Judnick uses AMSOIL Synthetic Chaincase & Gear Oil to protect his sleds’ chaincases.

“The chain and sprockets on our race sleds take a beating from the harsh landings and constant changes in snow and track conditions. With just routine maintenance, AMSOIL Synthetic Chaincase & Gear Oil prevents us from having parts failures in these areas,” said Judnick.

chain case oil

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Another team favorite? Mudslinger. It provides a protective, non-stick layer of armor against the accumulation of snow.

Mudslinger®

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Will Judnick go big this weekend? Be sure to watch his team live in action this weekend at the Seneca Allegany Snocross National in Salamanca, N.Y.