Oil is required to properly lubricate an engine and keep it running smoothly. But, it’s not quite that simple. Engine oil must be able to withstand high temperatures, provide shear and oxidation stability, and protect against aeration. In addition, it must be viscous enough to protect engine components but have a low enough viscosity to provide adequate fuel economy. And, the oil must be cleaned - meaning it needs to be filtered and replaced on a regular basis.
There are many variables related to engine oil that can affect an engine’s health, but maintenance in the form of regular oil changes (also known as oil drains) is key. How often the oil needs to be changed has a significant impact on a fleet’s maintenance operation, so extending that interval is essential to maintenance efficiency.
Engine oil basics
There are three basic ways to categorize engine oils: by viscosity, or the oil’s resistance to flow; by the primary base stock, whether the oil is mineral, synthetic, or a blend of both; and by the performance level of the oil, how it protects the engine, prevents wear, and protects against heat, shear, and aeration.
Viscosity
The most common reference to oil most are familiar with is viscosity. This is denoted by numbers, such as 10W-30 or 15W-40. The first number, before the W, which stands for “winter,” indicates the oil’s viscosity at 0 degrees Fahrenheit. The second number indicates the oil’s viscosity at 212 degrees Fahrenheit. The larger the numbers, the higher the viscosity.
Higher viscosity oils are heavier and typically coat the engine better to provide more lubrication and protection but can become overly viscous in colder climates. Lower viscosity oils work better in cold weather and also provide improved fuel efficiency but can become too thin to properly coat and protect engine components in hotter climates.
It is important to strike a balance depending on the conditions under which the vehicle will be operating, but the most important factor remains the engine manufacturer’s recommendation. Diesel engines, especially modern ones, are designed to operate with certain viscosity oils for optimum longevity and efficiency.
“For ages, 15W-40 was kind of considered the diesel viscosity grade,” says Dan Arcy, OEM technical manager for Shell Lubricants, a global lubricant supplier. “But as we started to move [to] lower emission engines, starting in 2007 to 2010, a lot of the engine manufacturers ... have switched over to 10W-30s or 5W-30s.”
Mineral oils, synthetics, and synthetic blends
Engine oil is also categorized into four groups by the natural gas and oil standards-setting organization, American Petroleum Institute (API). These groups, labeled I through IV, describe different levels of base oils, or base stocks, which lubricant companies use to create specific engine oil formulations marketed to businesses and consumers.
“Group I is the most fundamental and historically the most common base oil in the traditional mineral oil family,” says Brian Humphrey, OEM technical liaison for heavy duty at Petro-Canada, a developer and producer of lubricants. “This is measured by the amount of sulfur that remains in the oil [after refinement] and its viscosity index.”
The viscosity index is a measure of an oil’s change in viscosity versus temperature. The higher the viscosity index, the less it changes with temperature.
“Group I is the lowest,” Humphrey says. “Group II is slightly better on both of those properties: less sulfur, higher viscosity index. Group III is the highest of traditional mineral oil qualities. And then finally group IV are oils that are assembled from a singular type of chemistry molecule, the most common of which is polyalphaolefin, or PAOs.”
There is a Group V, which consists of all base stocks not defined by any of the first four groups. These are not used as base oils for engine oil, but rather as an additive to other base oils.
In the U.S., Groups I and II are considered mineral oils, while Groups III and IV are labeled synthetic oils. Technically speaking, Group IV is the only true synthetic, but Group III oils’ properties are within specification to provide the performance of a synthetic.
“A full synthetic ... the base oil that's in it is not something that's common or [occurs] in nature, it's a designed base oil,” Arcy explains. “The synthetic blend is really just ... a mixture of mineral oil and synthetics. A synthetic blend is really kind of a combination, it's kind of midpoint. You get some of the extra benefits of a synthetic, but not all of them.”
Humphrey adds that while there is no official rule, the oil industry typically agrees that a blend needs to include at least 30 percent synthetic oil for it to be called a synthetic blend.
Performance and technology: CK-4 and FA-4
The third way engine oils can be categorized is by performance - how well the oil holds up to extreme conditions. Modern diesel engines are designed to be more efficient and longer lasting than previous generations, so they have tighter clearances and closer tolerances, and tend to run hotter. It’s more important than ever for engine oils to be resistant to oxidation, shear, and aeration. CK-4 and FA-4 oils, the latest evolution in engine oil technology, were designed specifically to withstand these demanding conditions.
“The biggest change in the past few years has been the splitting of the diesel engine oil category into two separate categories,” says Kevin Ferrick, director of API product programs. “API CK-4 oils succeeded CJ-4 engine oils and are backward compatible diesel oils. Backward compatible means CK-4 may be used where CJ-4 … CI-4, CH-4, and earlier service categories are recommended. API FA-4, on the other hand, is new and intended for engines beginning with the 2017 model year.”
Ferrick says that while the two oils provide similar protection, FA-4s have lower viscosity grades to meet the needs of next-generation diesel engines and help improve fuel economy. He notes that CK-4 and FA-4 oils both provide improved oxidation resistance, shear stability, and aeration control over CJ-4.
- Oxidation. Oil oxidation is a chemical reaction that degrades the quality of the oil. “Oil oxidation is one of the main reasons for oil breakdown, and it occurs more readily under higher engine operating temperatures,” Ferrick says. “With many newer engines running hotter, CK-4 and FA-4 standards deliver improved oxidation stability versus CJ-4 oils.”
- Shear. As oil passes through the engine and is worked by different components, it goes through a process known as shear, in which the molecules are split apart, lowering the viscosity of the oil. This can have a negative impact on how well the oil protects the engine, leading to increased wear and potential damage. CK-4 and FA-4 oils have improved shear stability compared to CJ-4 oils, Ferrick says.
- Aeration. “As the oil is being whipped through the engine, it absorbs air,” says Paul Cigala, commercial vehicle lubricant application engineer at ExxonMobil, an international oil and gas company. “When those air bubbles are in tight places, they pop and ... can make marks on the metal surfaces and eventually can cause internal damage inside of an engine.” CK-4 and FA-4 oils were designed to release these air bubbles to avoid potential damage to the engine.
CK-4 and FA-4 oils are a clear improvement over previous generation oils, but it is imperative for fleets to use the proper oils in each vehicle. While CK-4s are backward compatible, FA-4s should only be used if the manufacturer specifically recommends it for the engine in question. When making the switch from previous generation oils to the new standards, it is important for storage and dispensing equipment to be properly labeled, and technicians to be properly notified and trained. See sidebar, Best practices when switching to CK-4 and FA-4 heavy duty engine oils, for more information.
Used oil analysis
Knowing which oil to use is one matter, but knowing that the oil a fleet is using is doing its job to protect the engine is another entirely. A good way to keep this in check is through used oil analysis, a process in which the fleet takes a sample of used engine oil from the vehicle and sends it to a laboratory to be analyzed.
Collecting the sample
During an oil drain, a technician must collect a sample of used engine oil to be sent in for testing. ExxonMobil’s Cigala cautions, however, not to take the sample from the drain pan.
“Live samples out of the engine block with a push-button valve that's either in the side of an oil gallery or somewhere where there's live oil flowing gives us the best results,” he says, noting that samples can also be taken using a length of new hose and a vampire pump through the dipstick tube.
“Take an oil sample when the engine is up to temperature [so] the oil has boiled off any condensation that's inside of the engine, and the engine has either just come in from the road or it's been warmed up,” Cigala adds. “Shut the engine off and pull a sample from the dipstick, or leave it running and pull the sample live.”
Analysis
Labs typically need two to four ounces of oil to produce accurate results, which are usually available about 24 hours after the oil sample is received. What are lab technicians looking for in these used oil samples?
“They're looking at a number of different properties of the oil and the chemistry of the oil,” Shell Lubricants’ Arcy says. “[They’ll] be looking at viscosity, they'll be looking at the different metals in it, and metals being broken down into wear metals and additive metals. We’ll be looking for, ‘is there iron in the oil from wear, or copper, or lead?’ Also, we'll be looking at the additive metals to make sure that the right product was in there, that someone [didn’t] put the wrong product in.”
The lab will also be looking for contaminants, Cigala confirms. Pollutants such as fuel dilution could be caused by a fuel injector issue or high idle situations, depending on the duty cycle of the equipment; coolants, potassiums, and sodiums from either head gasket or exhaust gas recirculation (EGR) cooler leaks; any kind of excessive wear metals, either from a lubrication issue or from contamination; silicon, which could be indicative of dirt entering through the air system. Anything that could be causing excessive wear inside the engine is flagged.
Results
Once a fleet receives the results of a used oil analysis, they can see if any actions need to be taken to improve the health of the engine or engine oil. If everything checks out, the regular maintenance plan can continue. If any items are flagged, however, action may need to be taken to prevent unintended damage to the engine.
“Primarily, you're looking at the viscosity level - it should be where it started,” says Petro-Canada’s Humphrey. “If it's moved away from where it started, either getting too thick or too thin, something's wrong. The additive levels should also remain stable. The oil is formulated with certain performance chemicals in it that have telltale metal levels: phosphorous, magnesium, zinc, calcium. Those are in there on purpose, and if the level of those additives changes dramatically from one oil sample to the next, somebody probably put a different kind of oil in there, so you've got cross-contamination.”
Used oil analysis is most useful when samples are taken at regular intervals, during each oil drain or even more frequently. As with most maintenance items, consistency is key.
“What you really are looking for is a change in trends,” Arcy says, noting that Shell recommends taking a sample during every oil drain, and being consistent with mileage. For example, if a fleet is performing oil drains every 50,000 miles, they should continue sending samples every 50,000 miles. “If you do a 50,000 [mile sample] and then a 30,000 [mile sample], your numbers are going to be different,” he says.
Paying close attention to oil analysis trends can help predict problems before they occur. Or, it can show that a result that seems out of the ordinary is actually normal for a vehicle in a certain type of service.
Selecting a vendor
There are many choices when it comes to selecting a vendor to perform used oil analysis. Some oil companies such as Shell (Shell Lube Analyst) and ExxonMobil (Mobil Serv) provide these services in-house. If a fleet uses oil from one of these manufacturers, the company will recommend using their analysis service. Other companies like Petro-Canada, for example, outsource analysis work to third-party vendors. Whichever a fleet chooses, there are a few factors to keep in mind.
- Location. If a fleet operates nationwide, its vehicles may not be returning to a home base for service, Humphrey says. In that case, the fleet would want to select a vendor with multiple locations across the country or even North America, so samples don’t have to be shipped as far for analysis.
- Reputation. “Do they have a good reputation among other fleets?” Humphrey asks. “Do people think their services are accurate and timely? Do they support you in an ease-of-use way? Do they have a nice, easy-to-use software system where you could look up the data on the lab from any computer, just log into the system and see your results?”
- Data access. Being able to easily access used oil analysis results and data is important for a fleet. “With everything being online on your smart device, everybody's connected 24/7, so to be able to have access to … the data 24/7 is what everybody's looking for,” Cigala says.
- Guidance. Fleets also need to look at what kind of guidance they will get that will be beneficial, Cigala adds. “You really want to have an understanding of who's going to help [you] understand and interpret the data to make it the most valuable for the fleet.”
Filtration
Though new oil technologies help keep oil stable longer and help hold oxidation at bay, oil still needs to be filtered to remove any foreign particles that could be harmful to the engine. Additionally, all oil eventually degrades, and when it does it can’t disperse fine contaminants as well, leading to agglomeration. This all needs to be filtered from the oil to keep the engine running efficiently.
Oil filter technology has advanced alongside engine and oil technologies, helping to improve vehicle efficiency and prolong oil drain intervals. Since CK-4 and FA-4 oils promise better oxidation and shear stability, and resistance to aeration, they may even help improve filter life.
“In the past, bypass filters were more commonly used than full-flow filters due to their ability to hold the higher amounts of sludge produced during engine combustion,” says Jay Stephenson, North America training leader at Cummins Filtration, a company that creates OEM and aftermarket filtration solutions for diesel engines. “However, engine improvements in recent years mean that today’s trucks provide cleaner combustion and tremendous improvements in fuel economy. As a result, these engines also produce less contamination in the oil than previous models.”
Stephenson adds that today’s engine oils contain better contaminant control properties and provide improved fuel economy, leading to less contaminants present in the lubrication system. In light of these advancements, full-flow filters are now more commonly being used.
When it comes to selecting the right engine oil filters, Stephenson says fleets should follow the same rules that apply to oil. Following the engine OEM’s recommendations, specifying the proper filter for the vehicle’s application, and using the highest quality oil available can all help a fleet get optimal performance and life from the oil filter. It’s about finding a balance between properly removing contaminants, storing these contaminants, and lowering oil flow restriction to improve fuel efficiency.
“When in doubt, talk to your engine, lube, and filter suppliers,” he adds. “They can help you make an informed choice about which oil and filter are best for your specific operation. A filter such as the Fleetguard LF14000NN with NanoNet media offers the most effective filtration design for today’s engines because of its ability to balance particle removal efficiency, contaminant holding capacity, and low-flow restriction.”
Extending oil drain intervals
When all is taken into account - advanced oils, oil filters, the technician’s time, vehicle downtime, used oil and filter disposal - oil drains are no small cost to a fleet. That’s why it’s important to be able to extend oil drain intervals as much as safely possible. The longer a vehicle can stay on the road without stopping, the better it is for the fleet. New engine designs, advanced oil technologies, used oil analysis, and filtration technologies are all working towards that goal. Advances made in the last decade or so have seen oil drain intervals increase to as many as 75,000 miles, compared to around 10,000-mile intervals 30 years ago.
Engines
Improvements in engine quality have allowed for longer drain intervals by keeping the oil cleaner.
“Engines have gotten better,” says Petro-Canada’s Humphrey. “Manufacturers are able to hold tighter tolerances, fuel injection systems are better, higher quality, higher pressures to atomize the fuel to get better mixing between the air and the fuel, primarily for lower emissions and better fuel economy. But a nice side effect is you don't contaminate the oil as fast so the oil can last longer on newer modern engines.”
Shell Lubricants’ Arcy notes that for most late-model vehicles, engine manufacturers have laid out oil drain intervals based on different criteria, such as a minimum number of miles traveled in the year or a specific fuel economy range. If fuel consumption for a vehicle is higher, it will have a shorter drain interval. If the fuel consumption is lower, it will have a longer drain interval. A vehicle will typically use more fuel when hauling a heavy load and the engine is working harder, so the oil needs to be drained more often. If the vehicle is hauling a light load, the engine is working less and there will be less fuel consumption.
Oils
The introduction and regular use of synthetic oils over traditional mineral oils increased oil drain intervals. Synthetics hold up better to extreme temperatures and therefore last longer between oil drains.
“[Synthetic oils] have pretty good properties when it comes to low temperature and high-temperature performance, so in general, they tend to be longer lasting fluids and higher performing fluids,” says Humphrey.
When CK-4 and FA-4 oils were introduced to the market in December of 2016, they brought even higher oil drain intervals with them. These oils provide even greater high-temperature protection, as well as the shear and oxidation stability, and aeration resistance discussed earlier.
“All the OEMs raised their oil drain intervals by 10,000 or 15,000 miles, pretty much across the board, with the new formulations that came out,” ExxonMobil’s Cigala says. “We're seeing opportunities for further optimization based on used oil analysis because the new formulations are so robust compared to CJ-4 formulations. Especially from an oxidation standpoint.”
Oil analysis
Perhaps nothing is more important than used oil analysis when it comes to extending oil drain intervals. If a fleet plans to extend drain intervals beyond the engine manufacturer’s recommendation, used oil analyses are imperative in ensuring the intervals are extended safely, without causing damage to the engine.
“OEMs kind of set a conservative oil drain interval based on what they see in field testing and performance across everyone's engine oils,” Cigala says. “Every customer's duty cycle isn't the same. We see opportunities for further optimization based on what we see in the analysis. We have a program built around that, called our Optimized Oil Drain Interval Process, where we look at … used oil analysis data and can predict what the end point of the oil is. [We] then move back to a safe margin, knowing that everybody is not going to change their oil exactly at the same time, giving them a cushion to allow them to safely run their equipment but get as much uptime as possible.”
Humphrey confirms that many of the OEMs who support these extended drain intervals mandate that fleets conduct oil analysis, at least on an initial trial basis, to be sure the extension is appropriate and safe for the fleet.
However, some OEMs do not support extended oil drain intervals, so it is important to check the terms of the manufacturer’s warranty before extending beyond the OEM recommendation. If a manufacturer doesn’t support extending drain intervals, doing so may void the warranty.
Filters
One additional factor that can help increase oil drain intervals is the filters used. New filter technologies have been developed to extend the filter change intervals along with the oil drain, all while removing contaminants from the oil to keep the engine safe.
“Fleetguard LF14000NN lube filters for the Cummins ISX15 and X15 engines are designed for 60,000-mile service intervals while offering a high level of engine protection over the life of the filter,” says Cummins Filtration’s Stephenson. “For fleets utilizing the Cummins X15 engines, the Cummins OilGuard [used oil analysis] program is an excellent way to know exactly what is going on inside your engine and may allow you to extend your lube filter change intervals up to 80,000 miles.”
Other new technologies, such as Cummins FleetguardFIT Filtration Intelligence Technology, provides real-time filtration monitoring. Stephenson says this uses integrated sensors and data analytics to give fleets visibility into filter and oil life.
Conclusion
Advancements in engine oil technologies have come a long way, especially in recent years. CK-4 oils have made large strides in longevity, providing resistance to oxidation, shear, and aeration, all while remaining backward compatible for engines before the 2017 model year. Meanwhile, FA-4s provide these same protections, delivered in a more fuel-efficient package for today’s engines and beyond.
Seeing oil drain intervals of 80,000 miles is something most people couldn’t fathom as recently as 10 years ago. But it is today’s reality thanks to these new oil technologies, used oil analysis, and new filtration solutions. It is always important to keep manufacturer recommendations in mind, however, and abide by them when necessary to prevent voiding the warranty. Whatever the interval may be, keeping up with oil drains is imperative to a fleet’s health.
