Uptime is life, and oil is an engine’s lifeblood. These two immutable facts intersect at oil drain intervals. The longer a fleet can go between drain intervals, the more uptime it can get out of a truck — and the more money both the fleet and the driver can make.
For fleet managers, that means they need to know how long they expect oil to last between drains — and how the oil’s interval point complements or conflicts with other preventive maintenance items.
Over the past couple of decades, oil drain intervals have moved out to longer and longer mileage points. But the trick is knowing how far you can safely push those intervals without compromising other PM items.
The obvious starting point is with your engine OEM’s oil drain interval guidelines.
“Many fleets actually have shorter oil drain intervals than what the OEMs recommend and are possibly shortchanging themselves on oil life,” says Steven Bowles, senior product specialist, Citgo.
So always check your owner’s manual for the recommended oil type and drain intervals. Some engine manufacturers allow longer drain intervals if the customer uses a specific oil analysis program.
The manufacturer-recommended drain intervals are based on the severity of duty and fuel economy. Severe duty/lower mpg applications have shorter drain intervals, while lighter duty/higher mpg applications have longer ones.
In fleet operations today, Bowles says, that translates into drain intervals of 50,000 and 75,000 miles being commonplace. Some OEMs allow up to 100,00-mile drain intervals in light-duty applications with an approved oil analysis program, he says.
“Always conduct oil sampling and have an engine’s oil analysis history before extending drain intervals,” Bowles says. “You might find out based on an engine’s oil analysis history that the oil is already at end-of-life at the current drain interval and can’t be extended.”
On the other hand, he says, you might see that all the parameters look good. If so, you can slowly increase your intervals while still monitoring the oil analysis.
Cummins launched its own in-house OilGuard oil analysis program in 2017.
“Our early OilGuard results provided the confidence to increase drain intervals for all customers from 60,000 miles at product launch to 75,000 miles for customers getting greater than 7 mpg,” says Kris Ptasznik, Cummins powertrain TCO and consultancy leader. Many customers participating in OilGuard were able to get their oil drains extended to 100,000 miles or more.
Why Oil Analysis Matters
“Engine oil is the lifeblood of the engine, so closely examining the characteristics of the oil can tell you a lot about the oil’s health and indicate mechanical issues with an engine,” says Karin Haumann, OEM technical manager, Shell Global Solutions.
“A regular oil analysis program also lets you build a historical database and watch for trends. Ideally, a sample of used oil should be analyzed after every oil change for every piece of equipment.”
Always take consistent oil samples using the correct equipment, procedures, and clean sample bottles, then get the samples to a lab in a timely manner.
Used correctly, Haumann says, oil analysis is a proven way to detect oil contamination or conditions in your engine that could cause premature wear and downtime. Shell recommends that oil analysis be part of a regular truck maintenance schedule, which can contribute to reduced total cost of operation.
Oil analysis should be thought of as a cost-effective early warning system, she says. “It can tell you important things about the health of your engine,” she adds. For example:
If analysis shows diesel fuel in the oil, you may need to check your fuel system.
Traces of coolant point to a cooling system that needs a check-up.
Too much dirt or soot could mean you’ve overextended your drain interval or have a leak in the air intake system.
“An oil analysis lab can notice minor abnormalities long before you may be aware of them,” Haumann says. “This will allow you to act before these early warning signs become possible operational problems or engine damage.”
PC-12 and Longer Intervals
Fleet expectations for longer drain intervals are now so baked into expectations that the next generation of diesel engine oils will be designed with them in mind, experts say.
Figuring out how to do so is the job of the American Petroleum Institute. Currently, it’s working with the Diesel Engine Oil Advisory Board and the Engine Manufacturers’ Association on the next standard of diesel engine oil.
Shell’s Haumann is chairperson on the API’s New Category Development Team working on the new formulation, dubbed PC-12. She says extending drain intervals is a key driver for the new oil category.
“The main consideration that determines oil life — and therefore drain intervals — is the oxidation stability of the oil,” she explains. “We have minimum requirements for oxidation in the API specifications, and the engine manufacturers design around those. And, luckily, there are things we can do that can increase oxidation stability and create a higher-quality engine oil.”
The development team is currently working on the specifications for PC-12, set for release in January of 2027 to meet the next round of U.S. Environmental Protection Agency Greenhouse Gas Regulations.
That increased oxidation stabilization to enable longer drain intervals dovetails with needs for the next generation of engines.
“Newer engines tend to be smaller, more powerful and run hotter, so oil oxidation control is an important aspect of newer oils,” Citgo’s Bowles says.
The current CK-4 oils tend to have about twice the oil oxidation life of oils meeting the previous API category, CJ-4. To determine initial drain intervals, he says, new PC-12 oils will likely use the same Volvo T-13 Oxidation test used to validate earlier oil categories. However, he believes the PC-12 test will feature tighter limits and longer oxidation life.
In addition, oxidation tends to cause sludge, varnish and thickening of the oil. So better oxidation control is important to maintain optimum oil viscosity and optimize fuel economy.
Beyond 100,000 Miles
If 100,000 miles between oil changes sounds amazing, then just wait, industry experts say. Now that the 100K barrier has been broken, there’s no telling where drain intervals are heading next.
Engine makers are paying attention, too. Beginning next year with Cummins 2024 engines, Ptasznik says customers will no longer be required to send in oil drain samples to extend beyond published guidelines.
“The lessons gathered from OilGuard generated an algorithm-based oil change monitor,” Ptasznik explains. “This monitor is embedded in every Cummins engine electronic control module to make oil drain recommendations on a truck-by-truck basis, maximizing the fleet’s uptime while protecting for the higher demand routes a fleet may run.”
Kyle Neumann, vice president of maintenance for Foodliner/Quest Liner, says his trucks are already at the 90,000-mile or 340-day mark when it comes to drain intervals — and he’s open to pushing those numbers out even farther.
“These longer intervals have no impact on our maintenance schedule, since we do ‘dry’ PM every 45,000 miles or 170 days,” he says. “Our PM form is certified by the DOT. So, we’re basically doing two annual inspections per year.”
Neumann has had an oil sampling program in place for over 15 years.
“We rely on that to dictate the oil drain intervals, along with guidance from our partners at Citgo. And if the data supports it, we will extend those intervals in the future.”
Look to Other Factors
“I think that the quality of diesel engine oils have reached the point that the oil itself is a non-factor in setting drain intervals,” says Darry Stuart, president of DWS Fleet Services providing limited-time executive maintenance services, and a former general chairman of the American Trucking Associations’ Technology & Maintenance Council.
Long noted for some takes on fleet management that go against conventional wisdom, Stuart argues that the primary driver for setting maintenance intervals now are other PM items that have to be taken care of, not oil.
“Ask yourself: When is the last time you saw an engine failure due to oil issues?” he says. “It never happens anymore. That’s because the oil is so good, and the engines are so tight, that it’s just not an issue.”
For those reasons, Stuart says he is now telling his fleet clients to set drain intervals around critical PM items and go from there.
“Set your intervals around your critical inspection points and the drivers’ hours of service,” he says. “Half the reason you’re doing [preventive maintenance checks] is to get eyes on the truck to comply with Department of Transportation regulations.”
Using that requirement as a baseline, Stuart says 50,000 miles is a good starting point between time and wear factors. But from there?
“You can pretty much go out as far as you want to,” he says. “Want to go to 80,000 miles? 90,000 miles? OK. Just make sure you’re doing your PMs in a timely manner and you’ll be just fine.”
With new engines and new oils, it seems like oil drain intervals will soon be pushed out even farther than seemed remotely possible just a few years ago. The main question seems to be how they will be slotted in with PM schedules and DOT safety checks. It’s all still very much a work in progress. But it seems likely that oil changes will become less frequent for fleets in the near future.