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AMSOIL Dealer alaska » Amsoil Information » All You Need to Know About Motor Oil Cold Flow

All You Need to Know About Motor Oil Cold Flow

Amsoil Protects your vehicle engine better

Cold Flow

Engineers agree that most engine wear occurs during cold starts. While the exact percentage depends on several factors and is difficult to define, the reasons include the following…SHOP AMSOIL

  • richer air/fuel mixture at startup washes oil from the cylinder walls
  • Condensation forms inside the engine that causes rust and corrosion
  • Cold piston rings and cylinders don’t seal as well, causing combustion gases to “blow by” the rings and contaminate the oil
  • 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 all these factors are important, lack of oil due to poor cold-flow properties is the biggest culprit. Fortunately, there’s something you can do about it.

“Cold” isn’t just for winter

First, it’s important to define a “cold” start. 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. Even in warm climates, cold-start wear is a problem.

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.

The problem is more pronounced the colder it gets, particularly if you’re using conventional motor oil.

Waxes solidify in the cold

Conventional lubricants contain paraffins, or waxes, that solidify when the temperature drops. These waxes cause the oil to thicken. In the comparison shown in the video, 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. If that oil were inside your engine on a cold morning, it could prevent the crankshaft from spinning fast enough to start the engine, leaving you stranded. Even if the engine started, you wouldn’t be out of the woods. Thick, cold oil can fail to flow through the tiny screen openings on the oil pickup tube, starving the engine of oil for several vital moments before the oil begins to heat up and flow throughout the engine.

In addition, thick oil can fail to flow through the tiny passages in the crankshaft to lubricate the main bearings. Similar oil passages in the camshaft ensure the engine’s upper end is lubricated. The further away from the oil pump these oil passages reside, the longer it takes the oil to reach components at startup, placing your engine at increased risk of wear.


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. The solenoid pictured above, from a Ford® 3.5L EcoBoost® engine, contains openings .007 inches across – about the thickness of two sheets of paper. Oil that fails to flow through these tiny passages reduces VVT performance and can trigger a check-engine light.

Here’s how to protect your engine

AMSOIL synthetic motor oils provide better cold-flow properties than conventional oils. Their synthetic base oils don’t contain the waxes inherent to conventional oils. As a result, they demonstrate reduced pour points and provide increased fluidity during cold starts. This translates into oil that flows almost immediately through the oil pickup screen and other tiny oil passages when you start your engine, protecting it against wear.

Look at the oil’s pour point to gauge its ability to flow quickly at startup, typically reported on the oil’s data bulletin. Pour point is the coldest point at which an oil will flow. Lower values equal improved cold-flow and maximum wear protection. AMSOIL Signature Series 5W-30 Synthetic Motor Oil, for example, provides a pour point of -50ºF (-58ºC).

Amsoil SEVERE GEAR®: Ultimate Cold-Weather Protection

Ultimate Cold-Weather Protection

AMSOIL SEVERE GEAR excels in hot and cold temperature extremes. By design, it resists breakdown from high heat, preventing acids and carbon/varnish formation. Its wax-free construction also improves cold-flow properties, improving fuel economy and cold-weather shifting.

For the ultimate cold-weather protection, trust AMSOIL


Some gear lubes fail to meet basic low-temperature requirements. Mobil 1 75W-140 Gear Oil, for example, failed to meet the requirements of the industry standard1. AMSOIL SEVERE GEAR®, on the other hand, delivers 20% more cold-temperature protection than the standard requires. It delivers better cold-temperature protection than Mobil 1 and Valvoline SynPower.

1Based upon results of samples of Mobil 1 75W-140 and Valvoline SynPower 75W-140 purchased in 2018 and tested in ASTM D2983 by an independent testing facility in May 2018. Samples sent blind to eliminate bias.
All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for use in the applications shown.

Combat the Effects of Cold Temperatures with Amsoil

Combat the Effects of Cold Temperatures

Vehicle maintenance is an important part of preparing for winter months. Extreme winter weather can make breakdowns especially dangerous, and most people aren’t aware of the effect cold weather has on conventional lubricants.

An oil’s cold-temperature performance refers to its ability to flow when the engine is cold, or below typical operating temperature (212°F), and not simply to what feels cold to humans – warm summer days are also cold to an engine. Startup lubrication is directly affected by a lubricant’s cold flow ability, and the impact is felt at higher temperatures than most consumers would think. For example, in early 1991, General Motors halted sales of the Corvette ZR-1. Eight engines had seized at its Bowling Green, Ky. assembly plant. The temperature had only dipped to slightly below freezing and, at startup, hard-to-pump motor oil did not reach the front camshaft bearings and they were destroyed by lack of lubrication. GM responded by requiring the use of synthetic oil in the Corvette.

Motor Oil

Most engine wear occurs at startup. Cold temperatures can render oil so thick it cannot flow through narrow passageways to protect critical components, increasing wear. The paraffins in conventional oil only worsen the problem. AMSOIL synthetic motor oils contain no paraffin, remaining fluid in frigid winter temperatures (down to -63°F) for easier starting, improved oil flow and excellent bearing protection. Their unique synthetic formulations allow them to flow in extreme cold and maintain high film strength in extreme heat for outstanding all-season protection.

Transmission Fluid

Transmission fluids are also affected by cold temperatures. Since transmission fluid’s ability to flow does not directly impact a vehicle’s ability to start, cold-temperature transmission fluid performance is not foremost in the minds of consumers. It is affected, however, and does impact performance and wear. Automatic transmissions can shift harder in the cold, but changes in transmission performance brought on by cold temperatures are usually more pronounced for drivers who operate manual transmissions. As transmission fluid thickens in the cold, the synchronizers in manual transmissions cannot spin as quickly as they need to, which can severely impact the driver’s ability to shift until the fluid is warmed enough to provide proper flow – and protection.

AMSOIL transmission fluids are wax-free and deliver extraordinary cold-flow properties. They help improve shift response, energy efficiency and warm-up times.

Gear Lube

Gear lubricants with high viscosity at cold temperatures are less efficient and the gears require more energy to turn, resulting in reduced fuel economy. Gears and bearings in the differential and axle housing are splash-lubricated, and gear lubricants that are too thick at cold temperatures can starve internal components of lubrication, which can cause failure.

AMSOIL synthetic gear lubes’ wax-free construction improves cold-flow properties for maximum fuel economy and smooth cold-weather operation.

Diesel Fuel

As the temperature drops, the wax naturally found in diesel fuel begins to crystallize. The point at which wax crystals form is known as the cloud point. These wax crystals eventually clog the fuel filter and starve the engine of fuel, preventing it from starting. While low-quality fuels may form wax crystals in temperatures as warm as 40ºF (4ºC), most fuels have a cloud point near 32ºF (0ºC). The point at which the crystals clog the fuel filter is known as the cold filter-plugging point (CFPP).

AMSOIL Diesel Cold Flow lowers the CFPP by up to 20ºF (15ºC) in ultra-low-sulfur diesel fuel (ULSD). It uses a jet-fuel-type deicer that disperses water to control ice formation throughout the fuel system. AMSOIL Diesel Cold Flow inhibits wax crystal formation, allowing fuel to flow to the engine more easily and improving diesel engine reliability in cold temperatures. AMSOIL Diesel Recovery quickly liquefies gelled diesel fuel and thaws frozen fuel filters in engines that haven’t been treated with Diesel Cold Flow.

Did you know?

AMSOIL Dominator® Coolant Boost significantly reduces engine warm-up times in cold weather. You can enjoy warm air from your vehicle’s heater faster on cold winter days by adding Coolant Boost to the radiator.

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