Synthetic Lubricants

By T. G. Schaefer

For most products, the word “Synthetic” is often a negative term, implying cheap, imitation, or artificial - just not up to the “real thing”. In the world of lubrication, however, just the opposite is true. Synthetic lubricants by virtually all measures are distinctly superior to their petroleum counterparts. And while they may be more expensive to buy, their cost saving performance benefits make them less expensive to use. In this market, Synthetic clearly means Premium.

Some definitions

Defining the term “synthetic lubricant” is becoming more controversial these days, but in general it refers to a lubricant or grease whose basestock has been manufactured by chemical synthesis or organic reaction, as opposed to being extracted or refined from naturally occurring oils. In many respects synthetics represent a different approach altogether from conventional petroleum based oils in that their molecular structures are custom designed and tailored to meet specific performance targets. To appreciate this concept better, we need to understand something about the composition of lubricants and how they work.

Most lubricants consist of a basestock and various additives selected to improve or supplement the basestocks’ performance. The basestock is the primary component, usually 70 to 99% of the finished oil or grease, and its properties play a vital role. To a great degree the structure and stability of the basestock dictate the flow characteristics of the oil and the temperature range in which it can operate, as well as many other vital properties such as volatility, lubricity, and cleanliness. Additives enhance these properties or impart new ones, such as improving stability at both high and low temperatures, modifying the flow properties, and reducing wear, friction, rust and corrosion. The basestocks and additives work together and must be carefully selected and balanced to allow the finished oil to do its intended job, which includes protecting moving parts from wear, removing heat and dirt, preventing rust and corrosion, and improving energy efficiency. Since the basestock is the dominate component with the most important role, one obvious way to make a better oil is to start with a better basestock. That is exactly what synthetic oils endeavor to accomplish.

Conventional petroleum basestocks or mineral oils begin with crude oil, a mixture of literally hundreds of different molecules derived from the decomposition of prehistoric plant and animal life. The lighter more volatile components of crude oil are stripped away to make gasoline and other fuels, and the heaviest components are used in asphalt and tar. It’s the middle cuts that have the right thickness or viscosity for lubricants, but first they must be cleaned up; undesirable components such as waxes, unsaturated hydrocarbons, and nitrogen and sulfur compounds must be removed. Modern processing techniques do a pretty good job of removing these undesirable components, good enough for well over 90% of the world’s lubricant applications, but they cannot remove all of the bad actors. And it’s these residual “weak links” that limit the capabilities of mineral oils, usually by triggering breakdown reactions at high temperatures or freezing up when cold. These inherent weaknesses limit the temperature range in which mineral oils can be used and shorten the useful life of the finished lubricant.

Synthetic basestocks, on the other hand, start from relatively pure and simple chemical building blocks which are then reacted together or synthesized into new, larger molecules. The resulting synthetic basestock consists only of the pre-selected molecules and has no undesirable weak links that inhibit performance. This ability to pre-select or design specific ideal molecules tailored for a given job, and then create those molecules and only those molecules, opens a whole new world for making superior basestocks for lubricants. In fact, the entire formulation approach is different: instead of trying to clean up a naturally occurring chemical soup to acceptable levels with a constant eye on cost, the synthetic molecular engineer is able to focus on optimum performance in a specific application with the knowledge that he can build the necessary molecules to achieve it. Since synthetics cost considerably more than petroleum based basestocks, they are generally reserved for problem applications where conventional oils fail, or where the efficiency benefits of synthetics recoup the initial cost.

A bit of history
The use of synthetic basestocks to solve lubrication problems is not new. Various synthetics were developed and used extensively during the second world war to prevent the oil from freezing in the army tanks during winter combat. After the war, synthetics were found to be essential for the new jet engines which ran too hot for mineral oils, causing them to burn off rapidly and leave deposits. These jet engines also had to be able to restart at high altitudes where temperatures were often -50°F, so the oil had to pumpable at very low temperatures as well as surviving the searing temperatures within the engine. Indeed the modern jet engine would not exist today if not for the simultaneous development of synthetic basestock technology in the 1950s, and today virtually every jet engine in the world operates exclusively on synthetic lubricants.

During the 1960s and 70s, synthetics moved steadily into severe industrial applications where they solved high temperature deposit problems with air compressors and oven conveyor chains, and low temperature flow problems in arctic climates. New synthetic chemistries emerged to meet and match every problem industrial users could create, and there were many! Gradually these expensive high-tech synthetic lubricants were entering the mainstream and taken seriously as they proved their ability to save money through reduced downtime, less maintenance costs, extended equipment life, lower energy consumption, and higher productivity. Focus shifted to the total cost of lubrication, not just the cost of the lubricant, and synthetics were often the winners.

Synthetic automobile motor oils were introduced in the early 1970s with such fantastic performance claims that they initially turned the auto manufacturers and oil companies against the new unproven products. While most claims were directionally valid, the level of improvements were often exaggerated to the point of fostering a “snake oil” reputation. Over the ensuing years, the true benefits of synthetic motor oils were identified and quantified to industry satisfaction and include better high temperature stability, improved low temperature flow characteristics, lower volatility, increased fuel efficiency, and extended life capability. Today car manufacturers and oil companies alike readily acknowledge the superior performance of synthetic motor and gear oils, especially in fleet or severe duty usage. For the average car owner, however, driving conditions are mild enough for conventional mineral oils to work satisfactorily, which raises the question of whether synthetic benefits are really needed for passenger cars and worth the higher price tag. In most cases the combined improvements will repay the higher initial cost, especially in severe duty applications, but since these improvements are not readily perceived by the driver, market penetration remains only a few percent after more than thirty-five years of active marketing. Synthetic motor oil usage will likely accelerate in future years as engine builders exploit the benefits in new engine design and ratchet up oil performance through tighter specifications.

In summary
Today the use of synthetic lubricants is accepted, widespread, and rapidly growing as their capability and cost efficiency benefits become better known worldwide. Jet aircraft use synthetic oils in the engines, hydraulic systems, instruments and landing gears; compressors use synthetics in the crankcase and cylinders; refrigeration systems use synthetics with the new environmentally friendly refrigerants; truck fleets use synthetics in the engine, transmission, and gear box; and the list goes on and on. Wherever a problem exists with mineral oils or a potential for improved cost efficiency uncovered, there is a synthetic lubricant ready and able to step in and lower the cost of total lubrication.