While some fleets strictly adhere to manufacturers’ recommended drain cycles, other fleet managers use various techniques to extend the interval between oil changes. This month, FE examines what savvy fleet managers should consider before “going long” on engine lubrication.
Fleets may save money by extending oil drain intervals, but how far is too far? What can be done safely that won’t jeopardize the engine?
On one side is the understandable and generally cautious position of engine OEMs and the oil manufacturers who don’t want to encourage practices that may jeopardize engine performance. On the other side are the economic and environmental pressures that are forcing fleet managers to look harder to find more dollars. It comes down to what is reasonable that still supports manufacturers’ recommendations. “As fleets, we have to make sure we are using everything to our advantage to keep our costs in line,” says Darry Stuart, president and CEO of DWS Fleet Management Services. “And we always pick on drain intervals.
“I don’t like the term ‘extending’ oil drains,” says Stuart. “I think ‘optimizing’ is a much better word” for the process and reasoning that he describes to justify adding miles to the interval.
There are many quality oils from which to choose, and the choice of oil may not be the determining factor in setting the interval. According to Stuart, “The most important thing about optimizing oil drain intervals is to make sure you have a PM [preventive maintenance] program that supports whatever interval you choose to use.” One of the key points to a quality PM,” he adds, “is to be consistent” and to audit the PM process to make sure that your people are performing the tasks and doing them the same way each time. Those items should be familiar: checking tire air pressure, load-testing batteries, pressurizing the coolant system, torquing wheel nuts and U-bolts, and greasing and lubricating the vehicle. “If those procedures are correct, then you can optimize your drain intervals,” Stuart says.
For the engine specifically, he recommends checking belts, idlers, tensioning, air restriction in the air filter, “and make sure you get maximum life out of your air filter.” Stuart points out that recently there has been some concern about fuel filter life and the quality of ultra low sulfur diesel (ULSD) fuel. “We are probably getting to a point where we’re going to have to increase our ability to filter the fuel in order to get to maximum oil drain intervals.” He notes that fuel filter life has been cut in half in some instances, for reasons not fully understood now. Stuart thinks the industry should consider additional filtration. He believes the capacity is available in oil and fuel, and “we could get to the mileage or hour or day intervals we’d like to achieve by having additional filtration.”
Engine oil is extremely complex, advises John Martin, whose career includes 33 years with oil and lubricant specialty additive companies. He says, “It does no good to extend a fleet manager’s oil change interval by a few thousand miles; you’ve got to take it to the next PM level,” because the truck is not being brought into the shop just to change the oil. Bringing the truck in costs more than the oil change, in terms of lost revenue. “So if a normal interval is 20,000 miles, and a fleet manager changes oil every 20,000 miles, he doesn’t want to go to 30,000 miles, he wants to go to 40,000 miles.”
What about using oil analysis to figure oil drain intervals? “Oil analysis certainly has its place,” says Stuart. “It tells of the quality of the oil as it relates to contaminants such as silica, glycol, and iron and copper wear particles.” But there are particular things in the oil additive packages that basic oil analysis does not pick up, Stuart warns. It may pick up a mechanical failure, but Stuart doesn’t use oil analysis alone to formulate oil drain intervals.
Martin agrees that oil analysis is important. “Basically, you’re analyzing oil for three different things: one is engine condition –– are you wiping a bearing and getting a high concentration of metals? Another is contamination –– are you getting a fuel leak or glycol leak which will eventually destroy an engine? The third reason is to determine the condition of the oil. Have you over-extended the oil? Are the additives still functioning?” The additives are the chemicals that enhance the performance characteristics of a particular base oil blend.
Some applications, such as extremely high or extremely low temperatures or severe-duty, can cause an oil’s base stocks to oxidize, but in most over-the-road diesel applications, the additive package depletes well before the base stocks are broken down.
Martin says modern oils contain as many as ten different chemicals in the additive package, including detergents, dispersants, and zinc compounds. The amounts of each are determined by the performance level desired, and these mixtures are usually a compromise to enhance some characteristic or another or to meet a certain requirement. Will the mix of additives and their durability provide the oil sufficient capability to extend the oil change interval? Only testing will tell, according to Martin. Oil change intervals must be optimized to provide maximum value to the fleet user.
Typically, diesel truck oils contain high concentrations of detergents and dispersants to keep the soot particles very finely dispersed throughout the oil so they won’t cause any wear damage. Detergent concentration is easily checked by doing a Total Base Number or TBN test, says Martin. TBN determines how effectively the oil protects against acids formed during the combustion process. The higher the TBN, the more effective the oil is over time or mileage. Dispersant concentration of an oil is harder to detect, although nitrogen content is a fair indicator. Soot concentration in the oil can be detected by thermo gravimetric (TGA) or light emissions (LEM) analysis.
The key point to remember about used oil analysis, Martin says, is that you’re looking for rate of change of an oil property more than absolute value. A fleet manager should obtain a baseline oil analysis and then sample his used oil frequently, say every 10,000 or 15,000 miles, and plot this data to tell when the oil is reaching the end of its useful life. Most additives’ properties tend to degrade slowly until the very end of their useful life. Then that oil property degrades rather quickly, according to Martin –– suddenly there is insufficient base number left in the oil. The detergency is depleted. The oil should have been changed immediately prior to this data point. This is one of the reasons field testing is so important, Martin explains.
“Everyone looks at soot particles,” says Stuart, “but they are much smaller in size than an engine’s internal clearances, so soot is more of an indicator of upper valve train wear than main rod or bearing wear, which everyone is more cautious about.”
Stuart adds, “When OEs recommended 10,000 to 12,000-mile intervals, some creative fleet managers were going 15,000 to 18,000 miles. When the OEs got to 18,000, there were fleet managers pushing 25,000 to 30,000 intervals,” which he notes is the average today. Some of the over-the-road fleets go up to 50,000 miles, supported by oil analysis, but that is controversial, Stuart says. More fleets are cautious instead of trying to find that leading edge. Some conservatively stay under 20,000 miles because they have no supporting PM, says Stuart. He suggests that if they enhance their PMs, they can get some quick dollars back, but “make sure you have a supporting PM program,” for any optimization. “You do have to look at total gallons of fuel burnt and idle time,” Stuart adds. “Because for every idle-hour, there’s a wear factor. Every hour is equivalent to 40 miles on the road, based on industry averages.”
What if you are running a mixed fleet and trying to optimize oil drain intervals? “It doesn’t matter,” says Stuart. He advises to set the intervals to a particular vehicle based on its vocation and work it is doing, and complement the system by checking gallons of fuel used, or the days, hours, or miles the vehicle is in use.
Oil consumption today is not an issue, according to Stuart. Tractors don’t use much oil today until they get into heavy miles. Even if the oil is burning, it’s a fuel. Usually, the driver tells you because it can reach a point where the oil blow-by causes a power loss.
If you optimize other lubes, it is easier to optimize oil drain intervals, according to Stuart. “We have solved the lube needs for transmissions and rear ends; we have quality oils available, and good quality greases, so it narrows down to procedure and the quality of your PM and what you do during your PM.
“Everyone is concerned with greasing the truck, and managers always want to use that as the reason why they can’t go to higher mileages,” says Stuart. “So they say they’ve got to grease drivelines and front ends.” He adds, “Drivelines can go 100,000 miles without greasing. So, if you set a drain interval for 30- or 40,000 miles and you use proper lubrication products you can go those miles, provided your procedure is correct.
“Come up with some mileage or fuel formula and stay consistent with it,” Stuart advises. “Stay within the 25-to 30,000 mile range, and if you have a good quality PM, you should always be within 10 percent.”
There has been a real push from oil companies on API CJ-4 oils, but fleets are not moving toward their use. There’s a cost factor involved, since CJ-4 oils are more expensive to produce. At the recent TMC meeting, Stuart learned that most fleets are staying with their current oil, mainly CI-4+. Even among fleets running ’07 engines, not all are moving toward CJ-4 oil. They are waiting to see how much impact it is having on the Diesel Particulate Filters (DPFs) cleaning/replacement cycle. Stuart found that quite surprising. Martin does not, since most fleets test extensively before changing any part of their operational formula, and these fleets are dealing with both fuel (ULSD) and lubes changes in the past 18 months. These fleets are more apt to incorporate CJ-4 oils after they understand completely what to expect of 2007 model year particulate traps and ULSD fuel.
The ’07 engines combined with CJ-4 oils will handle more soot and keep it in suspension. “If you choose to use CJ-4 oil for ’07 engines, you can use it in your earlier engines since it’s backwards compatible,” Stuart says, “I think you have to try to grab a few more miles between PMs and make sure you are using quality filters.”
The price spread between CI-4+ and CJ-4 oils has narrowed almost to being a non-issue. “If the CJ-4 oil is price competitive, I’d switch to take advantage of the higher quality and adjust the drain intervals accordingly. Make sure you have a high level of filtration and use good quality filters and maximize drain intervals strongly supported by a good quality PM program,” says Stuart.
“Changing oil puts fear into us about why we have to bring a truck into shop,” Stuart admits. It’s not a fear about having to look at the truck, he explains, but not changing the oil risks internal engine damage, “so fear forces us into compliance.” But he says fleet managers will be forced by economics to change their comfort zone and look at new dynamics to find more dollars, “and that’s absolutely going circle around the quality of PM.” If a fleet can optimize drain intervals at 45-to 50,000 miles, with great quality PM that supports it, and can remove one annual PM, that’s a savings. “But I don’t care what the interval is, it just has to be supported by consistent quality PMs doing the right thing.”
Darry W. Stuart also serves as the Technology and Maintenance Council’s General Chairman for 2007-2008. For more information, visit www.darrystuart.com/index.html.
