Oil analysis might be the best troubleshooting tool you have but very seldom use. It can help diagnose or avert mechanical problems, identify shortcomings in your shop, and it can even spot trouble drivers.
It’s always been useful but now, because of new low-emissions engines, particularly those using cooled exhaust gas recirculation (EGR), oil analysis is even more crucial.
With EGR, the engine relies on the cooling system to help reduce exhaust-gas temperature from around 650 degrees C in the combustion chamber to about 120 degrees C. In the process, the temperature of the coolant increases, which in turn heats up the oil. Crankcase lubes run about 22 degrees hotter than in older engines. Higher oil temperatures increase the rate of oil oxidation, a chemical reaction between oil molecules and oxygen (the oxidation rate doubles with every 10 degrees C). This reaction can make oil thicken and hard to pump. And that can mean a loss of power, poor fuel economy, premature ring and bearing wear, and formation of sludge in the oil.
Heat is not the only stress that EGR puts on oil. The lubricant needs detergents to neutralize the corrosive sulfurous and sulfuric acid present in recirculated exhaust gas. These acids are particularly problematic at low engine speeds — if you idle a lot or are involved in low-speed start-stop operations.
Controlling oxidation and neutralizing the acidic byproducts of the combustion process would qualify as heavy lifting in anyone’s book. But the retarded timing necessary to lower combustion temperatures further boosts the oil’s workload by raising the soot levels in the crankcase. Oils that don’t control soot well can give rise to several maladies, including valve-train wear, filter plugging, bearing failure, sludge, and loss of fuel economy.
Lube refiners have reformulated their products, increasing the level of basic additives as well as improving the base-oil quality to better control the damaging effects of EGR. We’re currently at the
CI-4 Plus oil performance standard and holding — the next one will come next year, before even tougher emission rules take effect in 2007.
High heat, acidity, and soot combined with new formations of oils mean that the old rules regarding oil-change intervals no longer apply. Engine manufacturers and refiners are changing those rules as they compile more data, especially with respect to extended drain intervals.
The stress on your oil and the consequences of downtime are convincing arguments for oil analysis — whether you run one truck or 1,000.
Most engine manufacturers and lube suppliers offer private-label oil analysis and are a solid first step. Typically, they contract the work to an independent lab like WearCheck Canada.
“Extending your drain interval is a good reason for oil analysis, but it’s hardly the only reason,” says Bill Quesnel, vice-president of the Mississauga, Ont., laboratory specializing in oil and wear particle analysis. “We spend a lot of time working with fleets to help them get comfortable with where their oil drain intervals should be,” he says.
Oil analysis takes away a lot of that mystery and allows you to look at information you need to make choices about how your equipment is maintained and take control over how to keep those costs in check, he says.
“Are you trying to maximize the life of the oil? Are you trying to establish regular maintenance schedules for your trucks? Are you running your equipment beyond your warranty and want to reduce the chance of major repairs? We can sell you test kits, but ideally, the customers who get the most value out of oil analysis are working closely with our technicians on an ongoing testing program that’s tailored to their business,” Quesnel says.
You want to take a sample from each truck in your fleet at its regular oil-change interval, which ideally should dovetail with your vehicle’s preventive maintenance schedule.
“Whether you’re a garbage truck fleet or a long-haul trucking operation, the best way to know what that point is, and whether you’re maximizing your change-out intervals, is by monitoring the condition of the oil,” says Quesnel.
WHAT TO TEST FOR
Engine manufacturers and oil suppliers offer change-interval targets. But it’s more practical to set your oil-change intervals based on your engine lubricant’s ability to maintain an acceptable level of viscosity, alkaline reserve additives (expressed as the Total Base Number), and oxidation.
Lab tests fall into four general areas of interest:
Total Base Number. Comparing your used oil’s reserve alkalinity (TBN) to that of new oil indicates whether your additives can neutralize acid residues. Says Quesnel: “When the oil is in service too long, the BN will drop. It can signal oxidation, an insufficient oil level, defects in the cooling system, the use of fuel with a high sulfur content, contamination. We can assess whether the oil is fit for further service.”
Contamination. Any engine lube will pick up contaminants. Caught early, dirt can alert you to the need to service the filters, saving the oil. Other contaminants signal other problems: water will cause the oil to form a sludge which can plug filters; fuel can indicate excessive idling or low compression; and glycol causes rapid oxidation of the oil and can lead to a major engine failure.
Viscosity. When oil loses viscosity, it gets thinner and vice versa. Oil analysis can show you why the oil is changing.
Component wear. Spectrographic analysis at the lab can show the presence of wear metals — aluminum, iron, chromium, and the like. The rate at which wear metal particles increase from sample to sample is as important as the quantity of particles in the oil. Regular sampling at specified intervals can establish wear-rate trends.
It’s important not to look at any one test result in isolation. For example, your engine manufacturer may have an acceptable soot level of 5 percent. If oil analysis tells you the soot level is 6 percent but viscosity is still okay, the TBN is fine, the oxidation level is not too high, and there’s no abnormal wear, you may want to keep running.
“As a maintenance manager, at least you can make a more informed decision,” Quesnel says. “The goal should be to use the oil as long as possible without incurring maintenance costs. The logic about how we make a determination is changing.”
WHAT’s the FREQUENCY?
Oil analysis is trend-based. To compare past results with current ones, you need a history — a trend line that lets you track metal wear and contaminants over the life of the engine.
Your first sample should be new lubricant that the lab can use as a baseline. Any time you switch to a different oil formulation or supplier, your lab needs to know about it.
Plan to sample at your regular service interval. If your goal is to extend your drain interval, test at the normal service interval and then in increments of 50 percent thereafter until the analysis shows the useful life of the oil is starting to deteriorate.
There are several ways to distinguish one lab from another, including price. Lab A may perform an array of tests for $11 a sample and Lab B will do the same for $14, but the more expensive option may deliver more. The value is in how they help you interpret the result and the level of service they provide.
Ask for a sample report. It should be concise, readable — in plain English — and convey data in absolute units.
Armed with that information, you can ask pointed questions of your engine manufacturer, lube supplier, or service garage.
Explains Quesnel: “If you approach your engine rep and say, ‘I’m experiencing some glycol leaks. Is that normal for this model of engine?’ you’re going to get a different answer than if you can say, ‘About 13 percent of this model engine are having glycol problems. What are you doing about that?’
“You may be a small fleet,” Quesnel notes, “but when you’re looking at results compiled from more than a half-million samples [from other fleets in the lab’s client list], you’re going to get some attention.”