A slippery situation
Research on grease intervals, formulations critical
By John Baxter
Today’s engine, oil, filtration and fuel technologies make extremely long oil change intervals practical, but grease and greased joint technologies have not always kept pace. Greasing intervals may at times synchronize with moderately long oil change intervals, but the best option may be a “dry” service interval that includes greasing between oil changes if warranted.
When determining greasing intervals, consider OEM recommendations from either the truck maker or the chassis parts supplier. Greasing is necessary not only to replace deteriorated grease but also – and more importantly – to purge dirt and water that have worked their way into the joint.
“You need to be conservative and follow the OEM interval because nobody can extend the interval without knowing what kinds of seals are used in the various components on the truck,” says Stede Granger, Shell Lubricants’ OEM technical manager, noting one component supplier might offer six different kinds of seals.
Central shop grease systems with long runs sometime create problems with congealed grease. A separate drum pump often is needed to get fresh grease to the location where greasing will be done. A follower plate on top of the grease in the storage tank may be needed to keep it separated from the air above; otherwise, air can be drawn through the grease when the level is low, limiting the amount of grease that actually gets into each component and its ability to flush out impurities.
One grease fits all
Fleets should demand a single grease appropriate for everything from wheel bearings to clutch throwout bearings, the requirements for which differ considerably. To determine a grease’s coverage, see if it has passed the ASTM D-4950-08 specification. Shell’s current recommendation for most fleets is a product with a lithium complex thickener such as its own Retinex LX NGLI No. 2, soon to be renamed Gadus S3 V220C as the company is changing its grease designations.
Fleets should demand a single multipurpose grease.
Mark Betner, Citgo’s heavy-duty lubricants manager, says attendees at Technology and Maintenance Council meetings often tell him that oil isn’t a problem, but that “grease is the weak link,” due mostly to pumpability. Choosing between NGLI No. 1 and No. 2 isn’t like choosing engine oil viscosity for cold weather; it’s all about where you do your greasing. If done in a warm shop, use No. 2; if you must grease outdoors and it gets cold where the fleet operates, No. 1 may be needed.
Citgo says the best compromise is a grease such as its own Syndurance 60 that uses a lithium-based thickening agent and a synthetic base oil that is thinner than that used in traditional formulations. “Such a grease will have longer staying power, and the synthetic base oil will help it pump,” Betner says.
Also ask the supplier how the grease has performed on the bench test and whether or not it has passed the synthetic corrosion test. Ask for physical evidence of what it can do, as reflected on the product data sheet. “Don’t just buy by price,” Betner says.
Jim Gambill, direct marketing specialist at Chevron Lubricants, says his company’s Delo Grease ESI NLGI 2 was formulated with the latest oil drain intervals in mind. While the average trucker is changing oil at more traditional intervals, many fleets are moving closer to 30,000-mile intervals. Not only does a grease need to be durable, it also must be able to be pumped in the shops to fill the various greased components on the vehicle. “Our early trials created a very durable grease that had difficulty pumping in cold weather,” Gambill says. “Customers demanded both durability and pumpability.”
The end product was Delo Grease ESI, a lithium complex grease with an additive chemistry and base oils to make it both durable and pumpable in cold weather. “The value is really in being able to align greasing intervals with wet service intervals,” Gambill says. This helps customers do most services in their own shops, which helps prevent mixing of greases or overgreasing. “Such a grease will even protect better if service intervals are skipped,” he says.
Technicians must fill a joint until fresh grease appears because greasing is largely about purging impurities that have crept in through the seals. With U-joints, make sure fresh stuff has appeared at all four bearings on each cross; if necessary, gently pry seals open at one point to observe.
When it comes to grease, it’s almost as important to please technicians as it is to satisfy OEM requirements. “If technicians don’t like the way the grease pumps into a fitting, they will complain or even return to a product that was used earlier that was easier to work with but did not perform as well,” Betner says.
A major concern is not having every grease job done in the home shop if the grease doesn’t hold up. Different greases may be chemically incompatible, possibly resulting in severely deteriorated performance. “Using a grease that lasts long enough for you to do it in your own shop every time helps solve this problem,” Gambill says. Also tell drivers exactly what grease should be used, he says.