Does Motor Oil Freeze? Conventional vs Synthetic Oils in Cold Weather

Does Motor Oil Freeze

Winter is coming. And for many motorists, that elicits concerns and questions about how their engine oil will hold up in frigid temperatures. Will motor oil freeze solid when the mercury plummets? Will starting the engine become more difficult? Could cold temps actually damage engine components without proper lubrication?

These apprehensions about motor oil performance in winter are definitely valid. When old man winter rears his frosty head, oil takes on properties that can negatively impact engine operation. So how cold is too cold for motor oil? And should you switch to synthetics to prevent issues?

Let’s warm up to the topic of motor oil in cold weather by first asking:

Does motor oil freeze?

Yes, all motor oils will freeze at some temperature. Conventional oils typically freeze around -15°F to -25°F. Synthetic oils freeze at even lower temps, usually below -40°F.

The key takeaway: Motor oil can and will freeze solid given cold enough ambient temperatures. But not all oils gel up at the same point. And the freezing process causes predictable changes in oil behavior.

This article will explore everything you need to know about the effects of cold on motor oil. You’ll learn:

  • The freezing points of conventional vs synthetic motor oils
  • Viscosity changes as oil cools down
  • Whether frozen oil damages engine components
  • Tips to prevent oil from freezing overnight
  • If switching to synthetics makes sense for winter

Let’s get fired up on the physics of frozen oil!

The Freezing Points of Motor Oil Explained

Motor oil freezes at the temperature where its chemical composition causes it to turn from liquid to solid. This transformation is referred to as the pour point or freezing point.

But that temperature varies based on what type of base oil makes up the motor oil:

  • Conventional motor oils use heavier, less refined crude oil distillates as their base oil. This causes them to freeze at temps around -15°F to -25°F (-26°C to -32°C).
  • Full synthetic motor oils utilize highly refined synthetic base stocks. This gives them lower freeze points around -40°F (-40°C) or below.

For example, a typical 10W-30 conventional oil may freeze around -22°F. A Mobil 1 0W-20 full synthetic may not freeze until -50°F.

Why do synthetics resist freezing more? The purified synthetic base oils contain hydrocarbons with uniform molecular sizes. This uniformity gives them better cold flow properties.

Conventional oil contains varying hydrocarbon chain lengths that are more prone to packing together into a frozen mass when cold.

To give a specific example, here are the pour points for two commercial motor oils:

  • Castrol GTX 10W-30 (conventional) = -22°F
  • Mobil 1 Extended Performance 0W-20 (full synthetic) = -54°F

So clearly, synthetics have a significant advantage when the mercury plummets towards zero or below.

Does Motor Oil Become Thicker as Temperatures Drop?

Absolutely. While not yet frozen solid, motor oil becomes more viscous or thick as ambient temperature drops.

This is due to physics. The hydrocarbon molecules in the oil pack closer together when cold. More tightly packed molecules make it harder for the oil to flow and take on liquid properties.

By design, multi-grade oils like 10W-30 perform well across high and low temperature ranges. The 10W viscosity grade means it flows adequately at cold winter temps. The 30 grade handles high heat viscosity.

However, near and beyond the pour point, the viscosity increase is exponential. The oil transitions from flowing liquid to semi-solid gel to frozen sludge.

Most oils double in viscosity for every -40°F (-40°C) temperature decrease. This exponential thickening makes it nearly impossible for frozen oil to properly coat, lubricate, and protect engine components.

To visualize this, 0W-20 synthetic oil at -40°F has the viscosity of 20 weight oil at 100°F. Then cool it down to -76°F and it has the consistency of 40 weight oil.

Will Cold Weather Cause Motor Oil to Gel or Turn Solid?

Yes, as covered earlier, motor oil inevitably freezes into a gel or solid at low enough ambient temperatures. This sludgy frozen state prevents the oil from flowing properly.

What exactly causes oil to freeze? Briefly, it has to do with the paraffin wax content. This waxy substance comprises 5-20% of the oil’s composition, originating from crude’s hydrocarbon molecules.

When cooled, the wax crystallizes first, then combines into larger lattices that eventually form a solid gel matrix. The other base oil components get trapped within this paraffin lattice as they also thicken.

Eventually every component of the oil congeals together in a semi-solid, sludge-like texture.

This waxy gel prevents the oil from flowing properly. The gel also can’t maintain the oil film on internal engine surfaces. So while not necessarily damaging in this state, the gelled oil loses much of its protective lubrication abilities.

Does Frozen Oil Cause Engine Damage or Hard Starting?

Motor oil turning to solid gel in cold weather can potentially have negative impacts on engine operation and durability:

Oil pump cavitation

Trying to pump sludgy, semi-solid oil can cause cavitation – bubbles forming due to insufficient fluid. Less oil volume and flow means less lubrication protection.

Difficult cold starting

Turning over thick gelled oil requires more battery/starter power. In extreme cold, the oil resists flowing to lubricate upper engine areas on start-up.

Increased engine wear

Until the oil warms up and returns to liquid state, engine parts like bearings and cylinders won’t have proper lubrication. This lack of oil film protection can accelerate wear.

However, some sources claim a short period with gelled oil on start-up isn’t overly detrimental provided warming follows. The starting sequences circulates sludgy oil back into a flowing state.

The main takeaways:

  • Solid sludge oil loses its lubrication abilities until warmed up again.
  • The thicker oil resists flowing properly when cold.
  • This can stress starting systems and reduce protection of engine internals.

Next we’ll cover some tips to prevent motor oil from fully freezing in the first place.

Tips to Prevent Motor Oil from Freezing Overnight

Ideally you want to prevent motor oil from ever fully freezing. Here are some tips to avoid sludged up, frozen oil:

Park in a garage

Obviously parking inside a garage protects the engine and oil from freezing overnight. If no garage is available, park facing east for morning warmth.

Warm up the engine

On very cold nights, run the engine for ~10 minutes before parking. This gets oil heated up and flowing.

Use an oil pan heater

Bolt-on oil pan heaters or dipstick heaters prevent oil from freezing in storage.

Reduce viscosity

Using thinner oils like 5W or 0W flows better in the cold. Lower viscosity grades don’t thicken up as drastically.

Change oil more frequently

Fresh oil has better cold flow properties. Opt for full synthetic oil changes every 5,000 miles.

With those tips in mind, does switching to full synthetic make sense for winter driving?

Should You Switch to Synthetic Oil for Winter?

Given synthetics’ improved cold flow properties, is upgrading from conventional oil the best plan for cold climates?

Here are the pros and cons of switching to synthetic motor oil for winter:


  • Much lower pour point than conventional oil
  • Still flows well in subzero temperatures
  • Easier cold starts, less wear when gelled


  • More expensive than conventional oil
  • Not necessarily required for most regions
  • Conventional may be OK with periodic warming

For most moderate climates with temps occasionally dipping below zero, synthetic oil is not absolutely necessary. A typical 10W or 5W-30 conventional oil still performs adequately during cold snaps.

Only consider full synthetics if:

  • You’ll be driving in bitter subzero temps regularly
  • The engine will be sitting unused for long periods in freezing conditions
  • Your wear prone engine could benefit from superior protection

For most folks, conventional oil changed 5,000 miles with periodic winter warm ups is sufficient. Take care not to start and run the engine until oil is flowing and up to temp.

But synthetics like Mobil’s Extended Performance line really shine if facing weeks of -20°F type scenarios. The cost is worth it for the added insurance against frozen gel damaging your engine.


Does motor oil freeze in cold temperatures? Absolutely. Conventional oils gel up at around -15°F to -25°F. Synthetics don’t freeze until -40°F or lower.

Below the pour point, oil thickens exponentially and turns to a semi-solid sludge consistency. This prevents proper lubrication and oil flow.

Trying to start an engine with frozen oil stresses the starter system. And lack of oil flow film means less wear protection on start up.

While not ideal, brief periods of frozen oil probably won’t catastrophically damage an engine. But steps should be taken to prevent it from occurring regularly.

Upgrading to full synthetics is recommended for drivers in frigid northern regions. But most areas can get by with thinner conventional oils and periodic warm ups before parking.

With this understanding of motor oil’s response to cold temperatures, you can confidently confront Old Man Winter without freezing or dangerously thinning your engine’s lifeblood. Stay warm and keep that oil flowing!

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