Moderation and control are essential when addressing the temperature of lubricants. In situations where the temperature level is too high or too low, a range of problems can quickly arise, from greases that stiffen and offer inferior performance to thermal degradation that can shorten an oil’s lifespan.
How does cold impact lubricants?
Cold temperatures can put stress on a lubricant, but the precise impact it will have will depend on its type and dedicated properties, with effects including separation, altered physical states and chemical degradation.
Lubricants that have a mixed base oil can sometimes separate into different phases, while those using a paraffin-type base stock may form into a gel. Lubricants often contain additives to supress or enhance properties that are native to the base oil, and these can also be impacted by lower temperatures. Cold may cause them to be rendered insoluble, which can result in settling and deposit formation.
Some additives, such as extra pressure and anti-wear inclusions, rely on chemical reactions caused by heat, and will struggle to perform if subjected to cold temperatures. As mentioned, greases can become too stiff, and oils may become far to viscous, making them circulate ineffectively. The knock-on effect on the machinery that the lubricant is assisting can be extremely harmful, with moving parts locked up, engines refusing to crank and gears failing to operate.
What are the effects of excessive heat on lubricants?
After exceeding its base temperature for activation, a lubricant will begin to oxidise, or degrade, twice as quickly for each increase of 10°C. Many of today’s lubricants have been injected with chemically formulated additives designed to help oils and greases function better under the extremely high temperatures they are subjected to.
There are an extensive range of issues for lubricants that are associated with circumstances where excessive heat is present. Too much heat can accelerate not just the decomposition of a lubricant’s base oil, but also any additives it has been infused with. While some additives may become volatile and transform into vapour, others designed to improve viscosity index may shear down swiftly.
Heat can also collapse protective oil films, leaving surfaces and other parts vulnerable to scuffing and abrasion from unwanted friction. Grease will separate far faster at higher temperatures, parting the thickening agent from the base oil acting as a lubricant. Although not in extreme heat, in warmer temperatures, contaminants in lubricants of a microbial nature can also flourish, leading to corrosion.
At greater temperatures, both grease and oil are more likely to leak. Over-heated lubricants can also have a negative impact on the equipment they serve – for example, a hot oil will reduce the life span of seals and filters and speed up corrosion. High temperatures can also result in the formation of gum and resin, interfering with mechanical performance.
If you can identify the perfectly balanced temperature for a lubricant, you will discover both an enhanced performance from the product in use and an extended service life.