The greater a lubricant’s viscosity, the greater pressure or load it can withstand, and the better it maintains separation between moving parts. If the viscosity is too high, it won’t flow as readily and your engine will work harder and burn more fuel.

A poise is the centimetre-gram-second (cgs) unit of viscosity. It expresses the force needed to maintain a unit… …still often used is the poise (1 Pa · s = 10 poise). At 20° C the viscosity of water is 1.0 × 10-3 Pa · s and that of air is 1.8 × 10-5 Pa · s.

Kinematic Viscosity: There is no named S.I. unit of kinematic viscosity (m2 s−1).

SI Unit of Coefficient of Viscosity The coefficient of viscosity η is defined as the tangential force F required to maintain a unit velocity gradient between two parallel layers of liquid of unit area A. The SI unit of η is Newton-second per square meter (Ns. m^ – 2) or. Pascal-seconds (Pa .s)

One of the most viscous liquids known is pitch, also known as bitumen, asphalt, or tar. Demonstrating its flow and measuring its viscosity is the subject of the longest continuously running scientific experiment, begun in 1927 at the University of Queensland in Australia.

Engine oil viscosity refers to how easily oil pours at a specified temperature. Thin oils have lower viscosity and pour more easily at low temperatures than thicker oils that have a higher viscosity. Thin oils reduce friction in engines and help engines start quickly during cold weather.

The owner’s manual of your vehicle should specify which oil viscosity you should be using for your engine. Often, the manual may specify multiple options to choose from depending on the weather. For example, it may recommend 5W-30 synthetic oil for warmer weather, and 0W-30 oil for colder weather.

The first number in the oil classification refers to a cold weather viscosity. The lower this number is, the less viscous your oil will be at low temperatures. For example, a 5W- motor oil will flow better at lower temperatures than a 15W- motor oil.

Similarly, SAE 10W-40 motor oil performs well in cold weather conditions. It has the same low-temperature limits as the 10W-30 but is better in higher temperatures. Either 10W30 or 10W40 for summer use is fine; however, 10W-40 motor oil will better protect your engine.

As a general rule, you’ll get the best protection in the summer when you use a slightly thicker grade of oil, such as a 10W30 instead of a 5W30. Engines need a thicker oil in the summer months because of the summer heat and its effects on thinning the oil out.

Designed for high mileage vehicles Mobil 1 High Mileage 10W-40 motor oil is recommended by ExxonMobil for use in high mileage vehicles (even those that have used lower quality conventional oils†), including: Cars. Trucks.

The lower the “W” number the better the oil’s cold temperature/cold start performance. The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100°C. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100°C etc.

Multi-grade oils could stay as close to the optimum viscosity over a range of temperatures – not too thick when it is cold and not too thin when it is hot. The difference between 10W-30 and a 10W-40 is the high temperature viscosity. Obviously, a 10W-40 is thicker than a 10W-30 at high temperature.

The smaller number, (the 20 part of 20w-50) describes how the oil behaves at 40 deg C and a 20w at 40 deg C is about 10 times thicker than your engine wants. A 10w-40 is better at around 6 times thicker and a 0w-40 is much better at about 4 times thicker.