IN PRINT — Fighting Friction: Educate yourself on oils and greases
Posted: March 9, 2017
How often have you seen a mechanic going from stem to stern on a truck with a grease gun and filling every fitting he can find with the same grease? It’s quick, cheap and easy, but that approach may not be the best option for the truck.
Oils, greases and other lubricants come in a dizzying variety of formulations and even colors and grades. Unless you’re on top of the oils and lubes game, it can be tough figuring out what’s best for your application. Those who understand the work lubricants do -probably would not take the one-grease-for-every-hole approach.
Jack Fasoli, national key account manager for Montreal-based Total lubricants, says his customers run the gamut from those that really understand and research the product to those that buy on price alone.
“Many think that one of the key -factors in choosing a lubricant is color,” he says. “Somewhere down the line they got it in their head that a specific color meant a specific grade or type of grease.”
Chassis lube, for example, can be -anywhere from brown to green to pink. Such a general-purpose grease is usually fine for mating parts where metal-to-metal contact exists, such as in steering kingpins or spring shackles, but it may not be appropriate for fifth wheels, Automatic Slack Adjusters or clutch throw bearings. The original equipment manufacturers make lubrication recommendations based on grades and intended applications.
Fasoli says fifth wheels, for example, require grease that won’t easily wash out with rain water yet protects the plate and smooths movement between the truck and trailer.
“There are three components to a fifth wheel grease – an oil for lubrication, and Extreme Pressure additive for pressure of the trailer on the plate, and a soap-based thickener to keep the grease in place,” he says. “If the oil washes out quickly, you’re left with a dry, sticky substance that can bind and accumulate dirt. When that scrapes away, you have no corrosion -protection, either.”
Based on that description, would you want that grease used in a sensitive part like a slack adjuster?
André Bolduc, senior technical–commercial advisor for Total says slack adjuster lubricants have special -requirements.
“Slack adjusters require a Grade 1 or 2 lithium-complex synthetic grease,” he says. “They should not be over-greased, either. Follow the manufacturer’s -recommendations.”
Transmission and differentials require lubricant too, and these are now usually specially formulated for the application. Recently, manufactures have adopted low-lube-level strategies as a fuel–saving measure (to reduce churning losses in the sump) or spray lubrication. These lubes are now almost exclusively -synthetic.
“Gear lubricant serves two purposes,” says Dale Kwasniewski, chief engineer at Meritor. “First it forms a hydrodynamic fluid boundary to prevent metal-to–metal contact. Second, the lubricant acts as a heat sink. Specifically, the gear oil -transfers the heat from [the] gear mesh and roller bearing interface to the surrounding carrier casting where forced convection [air flowing over the axle assembly] and conduction cools the oil and the process repeats itself.”
In regards to oil grades or viscosity, those fleets operating in warmer climates tend to specify multi-weight oil that will maintain a surface film, such as an 80W-140. Those fleets that operate in northern climates will specify -75W-90. However, the area of gear -lubricants is changing rapidly to address fuel efficiency and cold-flow viscosity, and new multi-weight gear lubricants are being developed to offer both cold-flow viscosity and maintain film thickness at high ambient temperatures.
“Using the improper viscosity gear oil could result in oil film breakdown, accelerating bearing and gear surface wear,” warns Kwasniewski. “All drive axles must use a gear oil with EP additives in order to contend with the contact pressure between the ring gear and pinion teeth. The use of anything other than an approved GL-5 EP gear oil will result in primary gearing tooth surface distress that can be easily identified as the result of the wrong lube.”
All Original Equipment Manu-facturers meticulously evaluate lubricants to ensure they are compatible with products and meet various test specifications.
“We require oil manufacturers to meet Dana SHAES256 specifications,” notes Steve Slesinski, director of -product planning for the -commercial vehicle market at Dana. “Truck owners must use these Dana-recommended products to maintain warranties on axle components.”
Other potential complications can arise from using non-approved lubes. According to Bill Gross, manager – -service solutions for Eaton, improper lube oil can affect the performance of components like transmissions.
“You’ll see reduced performance in the form of harder shifting in manual transmissions and longer shift times with automated boxes,” he says. “Worst case is shortened life and increased down time.”
Lubricants are part of the entire system these days. Component design teams work with the lubricant manufacturers very early in the design process. The lubricant is not an afterthought; it is considered an enabler for new technology. The decisions made throughout the design take the lubricant performance into account. Another lubricant may perform differently than the design considered.
“For instance, one consideration for pump sizing was based on the cold temperature performance of the lubricant,” says Gross. “If a different lubricant is used that does not have the same performance, the pump may not be able to pump the lube to the desired locations.”
If you’re not up on all the latest lubricant advancements, your dealer can help. There’s a lot going on these days, and component manufacturers are pushing lube suppliers for more. Don’t settle for a particular grease just because you like the color or because it’s a bit cheaper. You could be trading away thousands of kilometers of additional wear for a few pennies per Preventive Maintenance stop.
This fifth-wheel top plate has been gouged by material caught between the trailer and the plate. Note the -corrosion that’s forming due to a lack of lubrication.