Lubricants have come a long way since Roman chariot racers used animal grease to oil their wheels.

By Jack Beardwood

The advent of sophisticated equipment has brought the need to adhere to higher standards of lubrication - so much so, in fact, that it's fair to say that much of the machinery we take for granted would not be possible were it not for steady advances in both lubricants and their delivery methods.

The lubrication system is the lifeblood of your machine. If you abuse the oil, you are abusing your equipment. By examining the oil, you can learn the telltale signs of what's going on inside - hopefully before the machine needs a major overhaul. There's another side to this coin, of course. Knowing what's going on might even prevent you from wasting money by changing the oil too often.

"If you use the wrong oil or a lower-quality oil, you are probably going to compromise the effective design of the equipment because you are not going to get the full life that the engineers were trying to build into it," says Michael Rucker, marketing manager for Caterpillar Fluids.

Lubricant base oils are produced in a series of steps designed to enhance viscosity index, oxidation resistance, thermal stability, and low-temperature fluidity. The road from petroleum crude oil to lubricant is as follows:

Generally both solvent-refined and hydrocracked base oils are manufactured this way but differ in the processes used.

Group I, or conventional base oils manufactured by solvent refining, make up most of the base oil produced in the world today. Containing more than 0.03 wt. % sulfur and less than 90 wt. % saturates, they are less pure than hydroprocessed or synthetic base oils.

Group II and III base oils are manufactured by what the API calls hydroprocessing or severe hydroprocessing techniques. With sulfur contents of less than 0.03 wt. % and saturates contents of more than 90 wt. %, they are more pure than Group I base oils.

"The name petroleum is derived from the Latin petra - rock - and oleum - oil," explains Mark Smith, technical administrator for Analysts Inc. in Torrance, CA. "It was formed by the decomposition of organic refuse from ancient sea bottoms over a vast period of geologic time. As successive layers built up, these remains were subjected to high pressures and temperatures and underwent chemical transformations leading to the formation of hydrocarbons and other constituents of crude oil."

What's to Know About Oil?

A modern engine oil performs several important functions. The efficient operation of an engine depends on the oil to do the following:

1. Permit easy starting
2. Lubricate engine parts and prevent wear
3. Reduce friction
4. Protect against rust and corrosion
5. Keep engine parts clean
6. Reduce combustion chamber deposits
7. Fight soot
8. Cool engine parts
9. Seal combustion pressures
10. Be nonfoaming

Additives

To carry out these 10 basic functions, the base oil must be refined to the highest level possible and then compounded with chemical additives selected for their special characteristics:

Detergents. Usually metallic-based with the ability to clean up existing deposits in the engine and disperse insoluble matter into the oil, detergents control contamination resulting from high-temperature operation.

Dispersants. Usually ashless organic chemicals that control contamination from low temperature, they attach themselves to contaminant particles (such as soot) and hold them in suspension, preventing sludge and deposit formation.

Oxidation Inhibitors. These agents reduce oxygen attack on the lubricant base oil to lessen oil thickening and the buildup of corrosive acids.

Rust Inhibitors. Rust inhibitors protect iron/steel parts, such as lifters and pushrods, from oxygen attack.

Viscosity Index (VI) Improvers. VI polymers are like popcorn, exploding at high temperatures into long chain polymers that interweave and increase the oil's resistance to flow (viscosity). VI improvers must be shear-stable in the face of great stress or high temperatures.

Friction Modifiers. These chemicals form a chemical or physically bonded film that reduces the friction between the moving engine parts.

Antiwear Agents. Such compounds as zinc dialkyl-dithiophosphate break down to form a chemical film that eliminates metal-to-metal contact.

Corrosion Inhibitors. The combustion process produces acids. Corrosion inhibitors coat nonferrous metals, forming a barrier between the parts and their environment.

Foam Depressants. Detergent and dispersant additives can facilitate aeration, reducing lubricating efficiency. A foam depressant counteracts this activity.

Pour-Point Depressants. Base oils contain hydrocarbons that tend to crystallize into waxy materials at low temperatures. Incorporation of a chemical that reduces the size/rate of wax crystal formation can give an oil better low-temperature fluidity and, hence, a lower pour point.

The Magic of Numbers and Names

At the dawn of the automotive age, oils were classified simply as light, medium, or heavy, depending on their viscosity. As measuring capabilities improved, the Society of Automotive Engineers (SAE) developed a classification system based on viscosity measurements (see Table 2).

The development of VI improvers made the manufacture of multigraded motor oil possible. Multigrade motor oils, such as SAE 5W-30 and SAE 10W-30, are widely used because they are light enough for easy cranking at low temperatures but heavy enough to perform satisfactorily at high temperatures as well. Oil designations starting with the letter "C" (meaning commercial) pertain to diesel, while the letter "S" is used for standardor gasoline engines.

API Engine Service Classification

In 1970, the American Petroleum Institute (API), the American Society for Testing and Materials, and the SAE cooperated in establishing an entirely new API Engine Service Classification System facilitating the definition and selection of engine oils on the basis of their performance characteristics and the type of service for which they are intended. Both SAE and API systems are necessary to define an engine oil's characteristics.

Putting the Letters and Numbers to Use

Some people hold on to the shopworn concept that monograde oils are the best, says Mark Betner, manager of heavy-duty product sales for Citgo Petroleum Corporation. "In reality, monogrades do not do nearly as good a job as multigrades today. Modern heavy-duty diesel engines have a better life and are better protected by multigrade formulations. Monogrades could in fact cause more oil consumption, greater or more engine deposits, and cause higher wear problems - especially in cold weather."

Multigrade oil has polymers, which make the oil expand as it heats up. At startup it has a lower-viscosity composition. This allows for better flow, so the engine's lubrication system can deliver the oil to moving parts during the critical cold-start phase of operation where a major portion of wear takes place. After the oil warms up, its viscosity - and the ability to protect against thermal breakdown - increases.

Jim Burke, off-road marketing manager for Castrol Heavy Duty Lubricants Inc., says those faced with extreme operating conditions need to examine the oil's additive package. Long idles would have the potential to create excessive soot. In that case, you need a superior dispersant detergent. For heavy loads, you should examine the product's antiwear protection agents. For extreme temperatures, look into the kinds of oxidation inhibitors or antioxidants in your additive package. "Synthetics work well in extreme hot and cold conditions because they are less volatile and their oxidation abilities are naturally more stable."

For determining the highest grade in the generations of oil development, the highest letters in the alphabet determine the latest in quality standards. The first designation was CC. Before long, new formulations began to appear, such as CF-2– and CG-4–quality oil - the numeral designations distinguishing lubricants destined for two- or four-stroke engine applications - and after that it was CH-4. The latest API code is CI-4 for the tops in performance for four-stroke diesel engines. "It is going to give better wear protection, thermal stability, and deposit control than its predecessor, CH-4, which in turn gives better performance than a CG-4-quality oil," says Peter Van Benthuysen, technical advisor for Shell Lubricants.

SL is the latest designation for gasoline engine oils. "If they have a gasoline-powered piece of equipment, they have to be careful choosing oils because, in addition to the API service category, there are ILSAC [International Lubricant Standardization and Approval Committee] categories," he notes. "These are categories specific to recent-model, gasoline-powered, passenger-car engines with catalytic converters and their exhaust emission control systems. If you have these kinds of vehicles in your fleet, you want to choose an oil that meets not only SL but also ILSAC requirements. If you've got a heavy-duty gas-engine truck or other piece of equipment, you probably need just an SL oil, not with the ILSAC designation."

Using synthetic oils is a more expensive proposition but can provide some advantages, says Van Benthuysen. They have unusually good cold-temperature flow properties, permit easier cranking, allow for better flow at low temperatures than mineral oils, and flow more quickly through the engine. "They can get to the points that need to be lubricated on a cold start much more quickly. They also tend to transfer heat a little bit better because they do flow through the engine a little bit easier. They also have particularly good high-temperature performance that is resistant to oxidation and thermal breakdown. The oils stand up well in diesel engines for high-temperature performance." He says one common misconception is that by using a synthetic, oil drain intervals can automatically be extended. "There are certainly advantages to using synthetics over mineral oils, but an extended drain performance is not necessarily one of them."

An adept eye and a well-trained nose can help you detect problems early. "Changes in an oil's color or odor can be a sign of maladies," says Charles Gay, senior data analyst for Komatsu Oil and Wear Analysis. "Many oil-related contaminants might be visually detected in the field if the operator or servicer knows what to look for. Water, dirt, fuel, fuel soot, and wear debris may be detected in the field. However, if any of these conditions are noted in abundance, it's too late."

Gay says if an oil promptly turns dark after a change, there could be trouble on the horizon. The oil is oxidizing. Oxygen from the atmosphere is combining with the chemical structure, creating a near-burning process. Oxidation could be a sign of water in the oil, excessive heat, or excessive wear.

If the oil has a cloudy appearance, water is present. If coolant is in the oil in sufficient quantities, it will have a milky appearance and will be thicker, says Van Benthuysen. Fuel dilution would be discernible by smell. It would also result in a thinning of the oil. You could also smell oil that has been exposed to extremely hot temperatures. It would have a burning smell.

With regard to soot or debris, these would be noticeable on the dipstick or through your sense of touch. These will also thicken the oil. "If you can see debris or touch it, there is something seriously wrong with the engine," says Van Benthuysen. "I don't encourage touching used oil because it is a known carcinogen. If you are going to touch oil, you should have protective gloves on."

If you smell a rotten-egg odor, it could indicate decomposition of a chemical called dialkyl dithiophosphate, an antiwear additive and oxidation inhibitor, he says. "Some people will note that coming from the breather tube on a diesel engine. It could permeate the oil as well. Because it is a byproduct of decomposition, it is a very volatile gas."

The Only Substitute for Quality Is Higher Quality

With regard to crankcase oils, you should take the extra steps to make sure you get the best that is available within the specs, says Rucker. "Oil companies will usually have two or three different oils of that spec, and if a person is shopping for the cheaper oil, they will probably be able to save a few pennies but [will] get shorter engine life. The cheaper oil will have cheaper base stock and cheaper additives. They may meet the performance specs, but barely." He suggests consulting with the oil supplier to see if there is a higher-quality product available.

According to Rucker, a common mistake is simply not taking care when adding to or changing oil. "The biggest factor is dirt being put in with new oil. If you don't wipe off the filler spout or you allow the lid to stand open, you run the risk of contaminating the oil or fluid right there and then. Just because you've poured in new oil doesn't mean you're home scot-free. You need to be careful about grit and dust during transfer."

Whenever the oil is changed, it is imperative that the filter be changed as well. "As with your fluids, it's important that you use a top-quality filter," says Rucker. "We are finding a tremendous variation in the quality of filters and what they do. What can happen is, [if you] use a cheap filter, over time you get a buildup of sludge on the filter pleats and eventually some of it is released to find its way through the filter media."

Rucker suggests cutting open the filters after you change them and looking in the pleats to see if there are any large pieces of metal present. Filters might actually mask problems from oil analysis since they trap larger particles that could be coming from worn gears, bearings, thrust washers, or other wear-prone components. These materials should be bagged and shown to your mechanic or dealer for identification. "By the time they are big enough that you can see them, you are well on your way toward a failure."

One way to ruin a machine's oil is through poor operation habits, says Betner. Lugging the engine or upshifting below the proper rpm band can cause fueling problems that might include soot loading and fuel dilution (unburned gas getting into the oil), which can result in loss of viscosity and a variety of other possible problems. "If you don't have enough rpm, you don't burn fuel properly; if you don't have enough rpm with the loads you are trying to manage, you will burn fuel improperly and create more soot."

Betner also suggests making sure your service technicians receive training on how to properly take an oil sample, how to properly lubricate each fitting, and how to properly perform air filter maintenance. "There are still people who think they can take an air hose and blow out a filter," he says. "Most equipment manufacturers frown on that because you can do damage to the filter."

Knowing Is Better Than Guessing

Experts interviewed for this article say that an oil analysis program is essential to get the full life out of all your equipment's components and their lubricants. The process is inexpensive, extremely cost-effective, and responsive since most analysis labs post results on the Internet. Sample results that require immediate attention are sent via e-mail notification or fax.

"Oil analysis is probably the most important maintenance factor a person can have these days," stresses Rucker. "How can I have an X-ray to see what's going on inside my machine? Oil analysis is the way. Anybody who owns a piece of equipment with a diesel engine will benefit from oil analysis. The price of doing an oil sample compared to the price of a short engine life or a failure or the downtime resulting from it is just very small."

Oil samples will tell you whether you have a lot of dirt, wear debris, contamination, coolant, water, or fuel dilution. "One sample will tell you whether you have a sudden problem, but the more appropriate way is over time and then over the course of 6,000, 8,000, 12,000, 14,000 hours," says Rucker. "You see the trend in wear metals, you see the trend in how it is holding up over the oil-change interval, and you can get a much closer prediction of how much longer that engine or transmission will last before you have to overhaul it. Or you can spot problems, whether [it is] dirt entry from some source or a fuel leak. Sometimes you can spot a fuel injector problem from oil analysis."

Often neglected in oil analysis is the baseline sample, a sample taken within several hours of going back to work. Rucker says frequently after replacing a hydraulic pump or having the transmission open, the customers has a second failure. "The reason very often is that they put in dirt or debris. Go out and take another sample, send it to the lab, and find out if it is nicely cleaned up."

"A lot of people don't use oil analysis because, in all fairness, they have never been exposed to the right information about how to use it and what it can really tell them," observes Betner. "It must be done consistently so you can develop a trend. Whoever is doing your analysis can walk you through it. Make sure you know how to set up the program properly so you can use it as a preventative maintenance tool. Sometimes people just use it as a postmortem."

Among the information provided is a reading on wear analysis. "You will get the amount of wear metal that has accumulated in the oil during the compartment change interval. In the engine, iron is the most common wear metal. It comes from some of the critical wear areas; for example, the liner of the piston area, the crankshaft, or the camshaft. High levels of iron tell you that you are getting excessive wear accumulation in the critical areas of that engine. Another wear metal would be lead. That typically comes from the bearings in the engine."

Oil analysis will reveal the physical properties of the lubricant, including viscosity. "If you buy 15W40, you want it to come back as a 40 on the report. If it comes back 50 or higher, you can say that it has broken down, oxidized, had too much heat applied to it, and literally turned into varnish-type materials, or it's accumulated a tremendous amount of contaminants, such as soot," says Betner. If it slides down the viscosity scale and comes back a 30 or even a 20 weight, the oil has broken down. It's probably been contaminated heavily with fuel.

Optional tests include determining the total acid number and the total base number. "What is the acidic or corrosive condition of the oil? In other words, could that oil by the very fact of its time in use become acidic? Diesel oils contain sulfur, and that can break down in the oil and cause corrosive, acidiclike materials that can cause higher wear on an engine. So when you run a total acid number test or a total base number, that tells you how much protective your oil still has in terms of corrosive wear protection."

Betner points out that most oil analysis programs have a comment section where the provider will give its interpretation of the overall oil condition and an advisory as to what you should do in the way of maintenance practices.

Burke says a special test can be conducted within the oil analysis process known as particle counting. "You can measure the cleanliness of an oil by determining the level of contaminants. Particles over 2 microns can be detected. By closely monitoring the particle counts in a fluid, maintenance professionals can detect wear-causing abrasion at the onset. A typical oil analysis does not detect things over 2 microns."

Writer Jack Beardwood has more than 20 years of professional experience working with newspapers and magazines.

GEC - January/February 2003

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