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There are many different types of oil used within the automotive industry, and in fact, the industry has one of the widest oil uses of any industry in terms of variety. Automotive systems contain many complicated systems that require the different types of oil to function effectively. As with any oil, they can become inefficient and contaminated with time, so oil analysis methods are vital for the automotive industry.
Herein, we look at some of the different types of oil used in the automotive industry, namely lubricants, hydraulic oils, gear oils, and greases. This article looks at the common issues that can arise with each lubricant and the techniques used to analyze these potential problems and how the oils can be maintained to ensure longevity and efficiency.
Lubricants
Lubricants is a broad term, and is used within some of the other areas mentioned here, but are also used on their own in many other components of an automobile. These include in the engine, within the motor oil, in the transmission fluid, and for penetrating rusty components.
The most common potential issues associated with lubricants is the ease of which they can be mixed up and their ease of contamination. Many lubricant base stocks are very similar in terms of their viscosity and can easily be mixed up. Contamination is also commonplace as the lubricant is often splashed against various components and unwanted metallic atoms (the so-called ‘wear metals’) end up in the lubricant.
Because of the large number of lubricants used, and the various components in which they are utilized, there are many different methods used to analyze lubricants in the automotive sector. One, or a combination of, temperature-differential viscosity tests, direct infrared spectroscopy (IR), Fourier-transform infrared (FTIR), inductively coupled plasma (ICP), rotating disc electrode (RDE) spectroscopy, X-ray fluorescence (XRF), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) is commonly used in the analysis process.
Hydraulic Oils
Hydraulic oils are used within specific components and systems in an automotive vehicle, with them being found most commonly in automatic transmission and power steering fluid systems.
Contamination of wear metals is very commonplace for hydraulic oils, and depending on where they are used, can be contaminated from a range of other components, including bearings, servo valve plating pumps, pistons, cylinder liners, rods, spools, elastomeric seals, motor pistons or oil coolers.
Due to the high potential for wear metal contamination, elemental analysis methods are a common choice and can be used to measure the levels of chrome, silicon, lead, silver, titanium, vanadium, magnesium, molybdenum, and zinc – the most common wear metal contaminants from automotive parts.
As with any other oil in the automotive industry, hydraulic oils are prone to oxidation. Other methods to test the quality, state of oxidation, and long-term usability of a hydraulic oil include inductively coupled plasma (ICP), Fourier-transform infrared spectroscopy (FTIR), particle number and distribution, ferrographic analysis, proton-induced X-ray emission (PIXE), thermogravimetric analysis (TGA) and water content analysis.
Gear Oils
The oils within a gearbox, or gear system, are used to lubricate the gears under many stresses. If automobiles are used regularly, the wear on the gearbox and the oils can cause the system to become inefficient and can lead to sticking and breaking of the gears.
The constant stress and movements of gear systems, and the oils used, can lead to a variety of long-term problems if not carefully monitored and maintained. Alongside general wear and tear of the gears themselves from prolonged mechanical work, contamination from dust, dirt, and water in the gear oil is a common problem. Other contamination problems, such as from wear metals, are also common due to the contact that the oil has with the moving mechanical components. Oxidation of the oil is also a potential issue.
There is a myriad of tests available to ensure that gear oil is of high quality. These include carbon residue tests, channel point tests, chlorine tests, color tests, testing to see if a foam develops, flash point tests, copper strip tests, gravimetric analyzes, and measuring the oil’s concentration of insoluble pentane molecules, boiling range distribution, viscosity, acidic number, pour point, saponification number, sulfur, sulfated ash, storage stability, and nitrogen level.
Greases
Grease is used throughout an automobile and the automotive industry in general. There are also many different types of grease used depending on the component and temperature environment, with some of the most common being chassis grease, high-temperature wheel bearing grease, electronic grease, and white grease.
Each type of grease has its own properties and applications, with chassis grease (the most common type of grease used) being commonly used on the suspension and steering joints of an automotive vehicle; high-temperature wheel bearing grease is used in high-temperature frictional environments such as the disc brakes and wheel bearings; electronic grease is used on the electronic connections where heat cannot build up for safety purposes, and white grease is waterproof and is thus used on metal-metal contacts where water penetration is likely/a problem.
Grease is a messy and sticky substance and is thus privy to various issues, namely over-greasing, contamination, and the mixing up of different greases. In addition, a lack of knowledge from the user/applier and the common use of people using ‘all-purpose’ grease are other common problems. In the automotive industry, each grease has a different function for a given component/application and specific grease should always be used to maintain integrity and efficiency.
Grease can be analyzed in many ways, depending on the property being investigated. Common tests for analyzing the consistency of the grease include the cone penetration test and thermogravimetric analysis (TGA), whereas the investigation into the levels of antioxidants and additives in the grease are usually identified using differential scanning calorimetry (DSC). DSC can also be used to measure the remaining useful life of a grease. The viscosity of grease is measured by either using a rheometer or by undertaking kinematic viscosity tests and the contamination of grease is measured using either Fourier-transform infrared spectroscopy (FTIR), ferrographic analysis, or elemental analysis.
Sources and Further Reading
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