Does an oil's viscosity change over time?

if so how long does it take.Does an oil's viscosity change over time?
Depends on what you mean.





Does an oil's viscosity change over time when used (for example, in an engine or gearbox)? Yes - although the changes aren't necessarily predictable. Theoretically, as oil is used in an engine it will oxidise and the oil will thicken, it will also pick-up carbon from the fuel combustion and will thicken, and the engine will ';boil off'; light ends in the oil causing it to thicken. However the oil can also absorb unburned fuel which can - in the short term - cause viscosity loss. Also, if the oil is a multigrade oil with polymeric viscosity improvers the engine can ';shear'; the VI improver and thin the oil. So, an engine oil's viscosity in use is dependant on a balance of these effects and is, therefor, dependent on its chemistry, the engine's mechanical condition, running conditions, fuel type, etc.





Gear oils are a little easier to predict - they will thicken over time in use as the oil oxidises. VI improvers are normally not present and don't interfere.





If, OTOH you are asking whether the viscosity of an oil stored in a bottle or drum will change the answer is ';no'; - not in any way that will make a diffence to its use. You could store a gear oil or engine oil for 20 years and not see a substantial change - the oil may oxidise a little bit but the effect on viscosity will be negligable and, in all liklihood, the oil will have antioxidants added to it to block the oxidation anyway.Does an oil's viscosity change over time?
yes as it wears down and gas and dirt are absorbed into it...like in a car engine..
Oil when heated will become less viscous. dirt will make it more viscous. On its own, oil viscosity will not change with time. VIscosity is NOT a function of time.
yes as it gets worn it breaks down and doesn't do what it was intended to do....protect thats why you should always change oil in your car or truck after so many miles
in a motor the heat and the moisture that is moving through the environment make it change quicker
The short answer is yes, it does change. As to how long it takes, that depends on how much change you want to see.