Like the human body, a truck engine needs a checkup now and then to make sure everything is running smoothly. Testing a person’s blood can reveal high blood pressure, anemia or even a disease you didn’t know you had. Likewise, analyzing the oil in your engine can tell you if you have any engine problems developing and check the performance of your oil.
It’s the very best way to determine just how often your engine really needs an oil change.
The first step is to take a small sample that’s typical of the oil in the lubrication system – that’s the harder part. Then you send the sample to a lab. The lab will analyze it and normally tell you what the numbers in their report really mean. And the lab will red flag any critical problems. If you take repeated samples, you can easily learn to evaluate the numbers yourself.
Getting a sample
The toughest and most exacting part of an oil analysis from the trucker’s point of view is getting a good sample that is typical of what is in the engine’s oil pan. It’s not easy because, once the oil has been in the engine for any length of time, it consists of much more than the original lube. After so many miles, a complicated mix of liquids and solids the oil is trying to protect the engine against will have dissolved into it. Under the wrong conditions, a sample could include an amount of solid material, like wear metal or possibly even soot, that is not typical of what is in the oil, or even liquids like unburned fuel.
Lilo Hurtado, commercial vehicle applications engineer at ExxonMobil, says, “I can’t stress how important it is to get a clean, representative sample.” You’ve got to be on your toes throughout the process, says Hurtado, because “oil analysis is only as effective as the person using it.”
According to Shell’s Linda Pascali, a territory sales manager, the first step is always to get the engine hot, because the oil needs to be at operating temperature. The ideal time for analysis is after the truck has been driven and, says Pascali, “It’s always best to take the sample within 30 minutes of the time when the engine was shut off.” If taking a sample on a cold winter day, idling for 20 minutes might not be enough; drive the engine until the oil temperature gauge shows a normal reading – often 200 degrees F or more. Getting the oil hot enables the detergents to get the solids into suspension, the way they will be during normal driving. That’s what a “representative sample” really is.
Once the oil is hot, make sure the engine is shut off and remove the keys from the ignition. Check to make sure you have all the equipment needed to take the sample and that nothing is being re-used, says Pascali. Don’t even clean tubes or oil bottles with solvent and reuse. Even a trace of something from another engine can give false readings and make your oil analysis report meaningless.
The lab doing your analysis, often connected with your oil supplier, will give you a sample bottle and possibly other equipment. One common way of getting a sample is to capture something out of the stream of draining oil. This is much more easily (and commonly) done in conjunction with an oil change, as you’d have to reinstall the drain plug and then refill the pan anyway.
To get a sample this way, first prepare your sample bottle by removing the cap, place a pan under the engine and remove the drain plug. Don’t stick the bottle under the moving stream right away. Instead, give the moving oil some time to clear any solids that might have accumulated off the bottom of the pan and away from the drain hole. Pascali says the very best way to do this is to grab the sample when the pan has drained about half way. Experience from prior oil changes will tell you when about half the oil has been drained.
Shell uses a different system. Shell supplies tubing, and you can purchase a sample pump for about $30. These allow you to get a good sample without draining the pan even partially, a sample Pascali argues is superior to a sample taken from draining oil.
Steve Niemann, owner of Bellmawr Truck Repair in Bellmawr, N.J., showed us how to use the sample pump system:
1. Unscrew and remove the dipstick from the oil pan. Then grab some of the clear plastic tubing and run it alongside the dipstick. Mark a length of tubing that is 6 inches longer than the dipstick from where it sits on the top of the filler tube.
2. Using a sharp knife or pair of scissors, carefully cut the tubing square on one end and at a 45-degree angle at the other. The angle cut will help keep the tube from hitting the bottom of the pan and picking up too much solid material as the sample is gathered.
Note: In the rest of the procedure, be careful to keep the sample pump turned upward in its normal position. Otherwise the pump will become contaminated.
3. Insert the tube’s square end into the top of the sample pump through the center of the knurled nut. Push it in far enough (about two inches) that it drops below the pump a distance equal to about half the height of the bottle.
4. Tighten the knurled nut with your fingers to seal the tubing.
5. Install the sample bottle and then snug it up, while carefully holding the pump right side up.
6. Insert the other end of the tubing down into the oil pan through the oil filler tube. Try to insert the tubing about half way down in the pan. You can hold the tubing next to the engine to estimate length first, but don’t get the end dirty.
7. Once the tubing is down in the oil, hold the pump vertical and pump the plunger slowly just until oil starts to flow into the bottle. This will normally create a vacuum and allow the sample bottle to fill without further pumping. Pump one stroke at a time and only as necessary to fill the bottle to about two-thirds of the way to the top.
8. Next unscrew the bottle and install the cap.
9. Carefully wipe the hose off where it extends down into the bottle. Then loosen the nut, pull the hose through and out of the pump, and discard it so it will not be reused.
10. Cap the bottle tightly. Install the dipstick and screw tight.
11. Carefully fill out every item on the sample information form. Especially important are items like the engine type, brand and model, miles or hours and fuel usage since the last oil change, and type of service the truck sees. Specifying the exact oil in use is also critical. Hurtado stresses the need to include items such as oil consumption figures and miles on the engine. Without these, an analysis report may tell you very little. This is because acceptable numbers vary tremendously with all of these variables, especially the type of service. Unit identification is important if you run more than one truck. Make sure to include your phone and fax numbers so you can receive information right away if the lab uncovers a critical problem.
Another way to get a good sample is to use an oil-sampling valve, Hurtado says. The valve is typically installed in an engine oil passage just before the flow reaches the filter. A plug is often installed in the block right where the valve will be screwed in, making installation easy. Consult your engine dealer about where to install. Once the engine is hot, leave it running. All you have to do is briefly open the valve to get a good sample.
Reading the report
Once the lab performs the analysis on your sample, it will fax or mail you the report. Dan Arcy, product marketing manager, Shell Lubricants, told us how to read the report. “Don’t try to look at the detail numbers in the report first,” says Arcy, “because they can be very intimidating.”
1. Find a box giving a one-word summation of findings. On Shell’s report, it’s called the Status box and it’s in the top right corner of the report. You’ll see “normal,” “abnormal” or “critical.” In the second case, corrective action should be taken promptly, and with critical situations the truck should be brought in immediately for work.
2. Find a box detailing any recommended maintenance actions. Shell reports put this in a large area just below two lines that identify the engine and vehicle. On Shell reports, it reads, “Maintenance recommendations for lab no.” This part of the report tells you in plain language what the analysis found. It might describe the analysis results as “acceptable” or send up a red flag, saying, “analysis indicates critical component and lubricant conditions.” Further detail would then include mention of a problem such as fuel system leaks allowing fuel to dilute the oil, reducing viscosity and additive levels.
3. Finally, you’ll find a large box listing the numerical results of the analysis. On Shell reports, it’s labeled “Spectrochemical analysis in parts per million by weight.” The metals are listed in a logical order – for example, in Shell reports, listing wear metals first, then contaminant metals and finally, additive metals. Wear metals are worn off engine parts. Contaminant metals refer to items like dust, which enters the engine through leaky air intake parts and are foreign to the engine environment. Finally, additive metals are listed – such as those keeping the Total Base Number, or acid-fighting ability of the oil, up to snuff. Finally, contaminants such as fuel soot, fuel, glycol and other non-metallic contaminants, as well as measurements such as viscosity, will be listed.
What do the numbers mean? As Darcy says, “Trending is what’s important. Something changes, and you’ll notice.” Shell and most others typically list the last three to five reports with the most recent at the bottom. If the numbers jump up or down significantly, you have a problem; otherwise, you don’t.
If measuring results from increased change intervals, keep in mind that, prior to a change, wear metals rise directly in proportion to the miles. So, if increasing the change interval from 15,000 miles to 20,000, a 33-percent increase in concentration of a wear metal would be perfectly normal and indicate no deterioration in engine protection. But if wear metals had increased a given amount each 5,000 miles up through 20,000 miles, and then moved up at a greater rate from 20,000 to 25,000 miles, you should change after 20,000 miles.
