How Can a Heat Wave Affect Your Engine Oil?

How Can a Heat Wave Affect Your Engine Oil?

By on Jul 26 2016

Beat the heat before it beats you

As heat waves once again sweep our nation—continually expanding throughout the West and searing through the North—it is important to be mindful of the risks and potential dangers of such devastating heat. Heat is a powerful force (it can even prevent airplanes from flying!), so information is definitely power here.

When it comes to heat safety tips, we remind you to stay hydrated and to never leave children or pets unattended in vehicles, as hot cars can quickly turn deadly.

How often do you think about effects of heat, especially as it pertains to your vehicle?

The visual and somatic effects of a summer heat wave are easy to recognize—beads of sweat dripping off your brow, sunburned ears, ice cream melting faster than you can eat it, the familiar burn of fleshy thighs on a black leather car seat—it's a real treat, isn't it? But what about the cues that might be a little less visible? How do scorching temperatures affect what's under the hood?

How temperature affects your lubricants

Temperature affects oil, pure and simple. Generally speaking, temperatures affect an oil's viscosity which can, in turn, affect your automotive engine (you can learn all about viscosity here).

In the past, motorists would compensate for seasonal temperature changes by using different grades of oil during different times of the year: lightweight oils in cold weather and heavier oils in the hot temperature months. At the time, this was necessary to maintain proper engine lubrication. Extremely cold temperatures can cause the fluid to actually congeal, causing improper oil flow throughout the engine, and therefore not providing adequate lubrication; conversely, using an engine oil with too low a viscosity (particularly in high temperatures) would not provide sufficient film between the metal-to-metal contact.

Multivoscosity oils have made seasonal engine oils rather unnecessary, as they are specifically developed to operate within a wider temperature range thanks to Viscosity Index Improvers. VI improvers compensate for the range of temperatures to which an automotive engine may be exposed. An example of a common multiviscosity grade oil is 5W-20, where the "W" stands for "winter" and the lower "W" rating represents a lower pour point. The additives within these multiviscosity oils enable the oil to efficiently lubricate the engine upon initial startup, but reach manufacturer specifications by the time the engine reaches its operating temperature.

Extreme temperatures on either end of the spectrum can cause lubricant degradation.

Hot oil's best for frying potatoes

Lubricants don't really get better as they age, and heat only further stresses them out (causing the lubricant equivalent of fine lines and wrinkles, you could say). Svante Arrhenius, a Swedish scientist, won the Nobel Prize for Chemistry in 1903 when he discovered the relationship between temperature and (most) chemical reaction rates. The Arrhenius Rate Rule applies to lubricants in that once they have exceeded their base activation temperature, lubricants will degrade twice as fast for every 18°F (10°C) increase in temperature.

Oxidation is the most common reaction of an in-service lubricant (Machinery Lubrication has a thorough breakdown of what lubricant oxidation is here). Heat can accelerate the oxidation process on Arrhenius' principle, as mentioned above. Oxidation can cause a variety of problems for your engine oil, including viscosity increase, sludge and sediment formation, loss in foam control, rust formation and corrosion.

Other consequences of high temperature on lubricants include the following:

  • Additives may volatilize and escape into atmosphere
  • VI improvers shear down more rapidly
  • Microbial contaminants thrive in warm temperatures
  • Hot oil shortens filter and seal life
  • Accelerated corrosion
  • Both oil and gas more prone to leakage
  • Formation of carbonaceous gum and resins

Don't let your lubricants give you the cold shoulder, either

While it will probably be a while until we need to worry about freezing temperatures, knowledge is power!

These are some of the consequences of cold lubricants you should be mindful of come winter:

  • Blended base oils can undergo phase separation
  • Paraffinic base-stocks can become waxy and gel
  • Additives depending on heat-induces chemical reactions can fail to perform
  • Additives can become insoluble and settle, clot, and/or form deposits
  • Oil can become viscous
  • Engines may cease to crank/moving parts may lock up
  • Oil-lifting devices may fail to work

Play it safe

We certainly feel the burn during these record breaking heat waves, and we must always be mindful that temperature is always a powerful force, so take caution when dealing with such extremes. Be mindful of yourself, those around you, and your automobile: if you're planning a vacation, it's always a good idea to check your fluid's before starting that cross-country road trip€¦don't want to get stuck on the side of the road in the middle of a heat wave because of engine failure.


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