For the purposes of this article, I have used a broad definition of base fluids: oils that can act as lubricants on their own or can be improved by the addition of other components. This is not a definitive review – that would take a book to complete – but a look at some of the significant fluids that have been used and what has driven the need for these oils.

The history of oils for lubrication starts around 3500 BCE, as chronicled by the inventive Sumerians, who originated from what is now southern Iraq. Mention is made of the use of cedar oils, animal fats, vegetable oils and rock oil, also called bitumen, extracted from ground seepage oil springs. All of these were used for reducing the friction of the wheeled chariots that the Sumerians are credited with inventing.

Around 2500 BCE, the Egyptians are thought to have used olive oil for the sledges hauling the huge blocks of sandstone that were used to build the pyramids. The pharaoh’s throne was also wetted with olive oil to reduce the effort needed to pull it around.

For thousands of years after this, only a few innovations were made in substances used to lubricate, until the use of whale oils, especially from sperm whales, became more popular during the mid-1700s. The thriving industrial revolution needed an increasing volume of lubricants, especially for textile machinery. Sperm whales not only had blubber that could be processed but also had in their heads a huge reservoir of around 2,000 liters of an oily wax called case oil. This substance remains liquid even at subzero temperatures. Sulfur could be added to case oil to produce lubricants that were resistant to extremely high pressures.

Another product that emerged as a popular animal fat lubricant in the 1800s was tallow, produced from rendered beef or pork fat. This humble material was the spark that ignited the Indian Sepoy rebellion of 1857. It was rumored that tallow was used to grease the gunpowder cartridges for the Indian armys new rifles. The soldiers had to bite the ends off the cartridges to release the powder, and as they were covered in pig and cow fat, it was offensive to the Muslims and Hindus that made up the ranks, sparking the protest.

Tallow oils were also widely used until the 1950s, to lubricate locomotive and steamship engines due to its good lubricity and resistance to being washed away.

In 1859, the first oil well was drilled by Edwin Drake, in Titusville, Pennsylvania, and the rest is history.

The next 70 years, until the 1930s, was regarded as a time of technical progress, when inexpensive mineral oil-based fluids were used for lubricants. Improvements were made to the processing of crude, typically by boiling, with different levels of success as regards quality. It was not until the early 1930s that solvent refining finally produced the types of base oil that were needed for the ever-increasing car population, although even with this improvement oil drain periods were often less than 1,000 miles.

The quality of base oil was slow to change until the beginning of the 1960s, when hydrotreating was introduced. Adding hydrogen to the base oil at high temperatures and pressures in the presence of a catalyst produced more stable oils that were longer lasting. Eventually this led to further improvement with hydrocracking and hydroisomerization, which further removed impurities – especially sulfur – increased the viscosity index and provided better low temperature fluidity.

In order to categorize these new, different levels of quality, especially when used in engine oils, the American Petroleum Institute in 1993 created its well-known base oil group classification system. There are three types of hydrocarbon base oil, namely Group I, II and III, which provide increasing levels of quality and with different saturates, sulfur contents and V.I.s. These new high-quality mineral base oils, developed between the 1970s and 1990s, were developed in response to the commercialization of high-performance hydrocarbon synthetic oils.

These oils had their origins in processes developed by chemists Charles Friedel and James Crafts in 1877, but took until the 1970s to gain a significant position in the market for high-performance engine and industrial oils. They include polyalphaolefins produced by the catalytic oligomerization of olefins, defined as Group IV. PAOs are synthetic hydrocarbons but there was controversy in the late 1990s when it was determined in the United States that Group III base oils could be promoted as synthetic. However, in some countries especially Germany, synthetic base stocks are defined by law as PAOs or esters.

This leads to the other major API base oil category, Group V, which encompasses all other base fluids that can be used in engine oils. This was the original premise of the API – to aid interchange between different base oils when gaining approval against their engine oil classifications. Group V includes any form of esters, polyglycols, silicones, naphthenics and polyalkylene glycols.

Along with these more traditional base fluids, there have been many new developments in synthetic oils, especially for growing high-performance requirements, such as in the aerospace industry. Perhaps this could be the subject of a Base Oil Report in the future. Watch this space.