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We are in the middle of winter. Oil is sensitive to temperature. As such, winter has a big impact on the oil. Engine wear chances are greater when starting a car on a cold morning than any other time depending on the grade of the engine oil.

This is because some oil grades become thicker at a chilling temperature than at an operating temperature. Some oil does not flow easily in cold weather. Not every oil grade is good for cold season. 

The most important physical property of engine oil is called viscosity. In a lay man’s language, it is referred to as the thickness of oil. This property plays a major role in determining what oil can be used in certain temperature conditions. This is because oil viscosity is a temperature sensitive property. At high temperature, oil flows easily while at low temperature, it flows erratically.

This is not difficult to perceive as you may have seen some brands of cooking oil freezing at low temperature. For this reason, different climatic conditions have different types of engine oil blended for them.

Before the discovery of crude oil, animal fats and vegetable oil played a major role in lubrication of common equipment of those days which included chariots.

Polar bears, sharks and whales contain good oil! As early as that, it was observed that there was a critical relationship between oil and temperature. With the discovery of crude oil, engineers started blending crude oil based engine oil. However, the same phenomenon of temperature changing the physical character of oil still persisted much to the dilemma of industry players. From animal fats to vegetable oil such as soya oil and then to crude oil, the problem still persisted.

Following discoveries of how to control the impact of temperature on oil viscosity behavior, industry players felt that engine oil for winter conditions needed to be blended separately and oil for high temperature regions needed to be blended separately respectively. For winter based oil including the oil used at high flying altitude such as in aircrafts, a chemical which delays the freezing point of oil to negative degrees Celsius was the panacea. It solved the problem. The chemical additive is called pour point depressant (PPD). If this chemical was edible and put in cooking oil, cooking oil would not freeze at zero degrees Celsius.

In terms of classification, the Society for Automotive Engineers (SAE) elected that all winter based engine oils should be classified with a letter “W” at the end of a viscosity grade. For example, SAE 15W, SAE 20W, SAE 10W are engine oils for winter conditions. For high temperature conditions, the chosen standard was any grade above SAE 30. That is why we have SAE 30, SAE 40, and SAE 50 as engine oil for high temperature conditions. These are called mono grade engine oils. At that time, this classification was a major break through by the SAE.

The joy of the above discoveries and classification soon became truncated when it was discovered that with the advent of long distance surface transport, oil drains would become the order of the day each time a vehicle enters into a different temperature zone. For instance, trucks leaving South Africa for Zambia or Congo DR would need to drain oil somewhere before they enter Zambia due to potentially different temperatures. When returning to South Africa, the oil must be changed again. Further, in some countries with frequent adverse temperature changes, the potential to drain oil several times in a month became real.  The new research topic that emerged was how to come up with engine oil that does not change its thickness regardless of temperature.  Once again industry experts found a way of blending engine oils that would behave as winter based engine oils when it is very cold and behave like summer temperature based engine oils when it is hot. This discovery is one of the greatest gifts that the petroleum industry has ever given to humanity. This engine oil is called multi grade engine oil. Examples include SAE 10W/30, SAE 15W/40, SAE 20W/50.

The first part of the oil grade containing the letter “W” reveals that the oil can perfectly withstand winter conditions while the later part 30/40/50 shows that this composite oil can also withstand summer temperatures. This formulation has solved the above problem of choosing oil depending on weather conditions. If you cannot use a monograde oil with a “W” at the end of the oil grade in this weather condition, I recommend that you use a multigrade oil. Personally, I use multigrade oil.

In conclusion, I would encourage motorists to concentrate much on engine oils that are specifically blended to withstand hostile winter temperatures and summer temperatures such as the above multi grades. In winter, engine oil with a letter “W” in the standard is more appropriate.  In my personal opinion, thick oils such as SAE 40, SAE 50 are better for higher temperatures than for winter conditions such as the current weather conditions.

Thick oil such as SAE 40, SAE 50, SAE 60 suffers flow retardation easily in cold conditions. This may not be good for machines especially in cold morning weather when starting them. By the time the oil flows when you start the engine, the engine would have cranked already without adequate oil lubrication.

This promotes premature engine failure or seizure which is a drain on monetary resources and loss of production thereby reducing your personal savings and the GDP on national basis. 

*Johnstone Chikwanda is an energy expert and a Fellow of the Engineering Institute of Zambia, a PhD candidate at Johnson University, Knoxville, Tennessee, USA.


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