If you have ever deposited a quantity of oil, whether it be from Shell, Fuchs or Mobile, into a drum or storage container, only to come back weeks or months later and find that the container is much lighter than it was, you are not alone. Oils of all kinds are subject to evaporation, although some suffer more than others, which means that the volume of oil will decrease over time.
Although this is not usually a problem, in some circumstances evaporation loss can have very serious consequences for your machinery. For that reason it is important that you know how to spot the signs of evaporation loss of engine oils, and the things that cause such losses.
What causes oil evaporation loss?
The problem of oil evaporation can be caused by a number of circumstances, but one of the most common is the oil drum itself. Despite what most people think, oil drums when sealed are not always completely airtight. If they are kept in an area with constantly changing temperatures, they become ‘breathable’ and air can get in or out through the bung plugs. Similarly, if the sun is allowed to heat an oil drum, it can cause the oil to evaporate.
Of course, this is something that is quite rare but it can and does happen, which is why it is a very good idea to store oil in strictly temperature-controlled rooms. There, they will not suffer from extreme changes in temperature.
How to spot evaporation loss
Obviously, the simplest way to calculate evaporation loss is by weight, but a change in the weight of an oil drum is not always evident; after all they are not picked up and moved around all that much in most cases. Luckily, it is also possible to visually spot the signs of lubricant evaporation. For instance, when evaporation occurs, remaining lubricant is likely to have changed in terms of viscosity, with the lighter, smaller molecules changing first, thus causing viscosity to climb higher.
As well as being possible to spot, this change in viscosity can also cause machinery to lubricate itself less effectively, which can cause a range of issues such as a restriction in oil flow, which could tip you off to the problem.
So, although oil can experience evaporation loss, it is not likely to be a huge problem, unless you notice very obvious changes to your oil and your equipment.