5w40 vs 15w40 – Difference and Comparison

What is 5w40?

The 5w40 Oil is a natural motor engine oil. The 5w40 Oil is named after its ability to adapt to the needs of the engine. In other words, the name is essentially implanted together with a description of its beginning to the specified method of oiling the engine The 5w signifies winter, thus the oil must have a maximum viscosity or flow at low temperatures. Its viscosity at 0°C is 5, and its viscosity at 100°C is 40. 

The weight or viscosity of the SAE engine oil is represented by the two values on the 5w40 oil for which engine. The resistance of the fluid to flux is known as thickness: the larger the amount, the better the resistance of the liquid to change, or the more significant, the thicker the fluid. Multi-grade oils, such as 5W-40, have a viscosity rate of 5 at 0 degrees Fahrenheit and viscosity properties of 40 at 212 degrees Fahrenheit. Oils come in a variety of grades. The “W” indicates that the first number is the “cold” or “winter” ranking.

The oil reacts to temperature by thickening when cold and thinning when humid. When a motor is cold, one-grade SAE oils are either too dense to effectively lubricate it or too dry when it reaches operating temperature. Oil manufacturers use thin base oil additives to make a 5W-40 oil behave like one-oil with a 5-oil cold grade, but when the oil heats up, it behaves like one-oil with a 40 rating.

What is 15w40?

15w40 is made for older engines that run on higher Sulphur fuels (500 ppm and above). It is backward compatible with prior API Oil Categories and can be used in over-the-road diesel trucks, off-highway diesel equipment, agricultural tractors, and passenger cars and light trucks with diesel, turbo-charged diesel engines, or gasoline engines.

This product offers high soot dispersancy and wear control, and it also provides superior protection against wear and corrosion. Due to its superior formula, it has reduced sludge formation, inhibited varnish formation, and exhibited exceptional anti-oxidation properties as well as high-temperature stability.

15w40 engine oil also denotes a specific potential. The 15w40 engine oil is multi-grade and mineral-based. The term with distinct letters and digits defines the oil kind. The 15 represents the lowest temperature, and the 40 represents the viscosity in centistokes. Because the oil is durable in both winter and summer, it is classified as a multi-grade oil. With a high-performance system within the engine, the oil is given a performance additive package. The oil’s viscosity index is the same as SAE 15Wool at cold temperatures. Both diesel and gasoline engines require 15W40 multi-grade motor oil.

Difference Between 5w40 and 15w40

  1. Viscosity: The viscosity of the two engine oils varies, affecting their sensitivity to weather. Viscosity means thick, sticky, and semi-fluid in terms of flow. The 5w40 engine oil specifies a maximum viscosity level of 5 degrees. It flows smoothly in these cold temps. I mean that the oil flows well in cold temperatures. The 15w40 engine oil stipulates a minimum flow temperature of 15 degrees within the engine. It flows at low and high temperatures, making it a multi-grade engine oil.
  2. Detergents: Because of its nature and lack of availability on the market, 5w40 engine oil contains no detergents (CARBIBLES, 2019). The 15w40 engine oil contains detergents in its state. Because mineral oil contains such particles, it must be purified before use. Detergents are in 15w40 engine oil.
  3. Fuel economy and price:  Due to its nature, 5w40 engine oil is scarce and hard to come by. Due to its single grade and non-availability, engine oil is not a major economic factor. Due to its multi-grade nature, 15w40 engine oil is widely available in the market. Because 15w40 engine oil is multi-grade, it is inexpensive and may be used in both gasoline and diesel engines.
  4. Temperature range: To avoid being turned into the fluidity form and therefore damaging its viscosity levels, 5w40 engine oil is used at a maximum of 5 degrees. It works in cold weather. The 15w40 engine oil plays well at temperatures up to 15 degrees, making it suitable for both winter and summer use.
  5. 5w40 is cleansing and leaves no deposits on the engine, whereas 15w40 is suitable for cars whose engines have worn out due to constant use.

Comparison Between 5w40 and 15w40

Parameters of Comparison5w4015w40
ThicknessRelatively thinnerRelatively thicker
Range of TemperatureBetween -30 °C (-22 °F) and +40 °C (104 °F), 5w40 is utilized.In the temperature range of -20 degrees Celsius or -4 degrees Fahrenheit to +40 degrees Celsius or 104 degrees Fahrenheit, 15w40 is suitable for usage.
SuitabilityIn cooler climates, 5w40 performs well.In a hotter atmosphere, 15w40 is preferable.
Range of usageWideNarrow
Specificity of Engine5w40 has a broader range of applications.15w40 is frequently used in engines with more than 60.000 miles on them because it provides better engine protection.


  1. https://www.sae.org/publications/technical-papers/content/2002-01-2769/
  2. https://www.sciencedirect.com/science/article/pii/S0301679X10001854