Know Your Fluids: Oils
Flowing through the big, powerful engines of work trucks are substances of little comparative size but great might: fluids. Fluids are key to maintaining the health of a fleet; oil keeps the engine lubricated, coolants moderate temperature, DEF reduces emissions, and additives ensure peak performance.
Find out if your fluid knowledge is current as we answer the fundamental fluid questions.
Part one of the three-part series on truck fluids is all about oil. Not only is oil critical to engine health, it’s also an ongoing fleet expense. Making the right choices about which oil to use, when to change the oil, and using the right filter can help fleets strike the appropriate balance between cost and operating a well-oiled fleet (literally).
If you want a simple answer, it’s this: Use the oil recommended by the OEM.
“The No. 1 fundamental about oil is to understand the oil requirements for each vehicle’s engine,” said Stede Granger, OEM technical services manager for Shell Lubricants. “Your OEM representative or their website and your owner’s manual are good sources of information to be sure you’re choosing the right oil.”
Although the recommended oil may be a little pricier, Michael Middleton, core services manager, customer experience for Valvoline Instant Oil Change, said avoiding the temptation to use a lower grade oil actually pays off.
“Understanding the requirements from the manufacturer that the oil must meet is critical to ensure proper functionality for the truck. Don’t try to cut costs on using a lower grade oil,” Middleton said. “Work trucks are just that — work trucks. Giving them an oil that can meet the high demands on a work truck will benefit them in the long run. Fewer engine problems means less money spent on repairs and less downtime for a work truck off the road.”
But, let’s say you’re looking for an oil that can be used across a number of models in your fleet. In this instance, according to Granger, it’s important to be mindful of fuel type.
“In general, there is a difference between the oil used for diesel and gas engines. You don’t want to use gasoline oil in a diesel engine,” he said. “But, sometimes you can use diesel oil for both engine types. For mixed fleets with both diesel- and gasoline-powered trucks, it can be easier to use one engine oil fleetwide.”
It’s important to work with your lubricant supplier and OEM to help you identify the oil that offers the best performance for your engines, Granger said.
Scott Killips, CEO, HUBB Filters, said fleets can choose from a wide range of oils that are suitable depending on the specific application.
So, how should fleets narrow it down?
“Choosing an oil that is API-certified will help ensure that the oil will perform as advertised,” Granger said.
Killips also said proper engine lubrication is about more than what oil you choose.
“It’s not just the oil; it’s the oil and the oil filter because they work together in the vehicle’s lubrication system,” he said. “Compare it to the human body where the kidneys filter the impurities in the blood. In both cases, they work together and one can hold the other back if it does not function the way it should.”
Alt-fuel vehicles may have slightly different oil requirements, according to Dan Holdmeyer, industrial and coolants brands manager for Chevron.
“Briefly speaking, switching to compressed natural gas (CNG) or liquefied natural gas (LNG) may require an engine oil designed to handle the higher temperatures generated and the engine modifications made to run those fuels,” he said. “Switching to a biofuel will require specific fuel system maintenance and potentially fuel additives tankside, depending on the level of biofuel but check with your fuel supplier first.”
A common misconception about oil is the numbering system for viscosity grade, Granger noted.
“When people see 5W-40, they often think the ‘5’ means it’s too light for a work truck engine, but that number doesn’t indicate how well the oil is lubricating the bearings. The number on the left actually tells how well the oil performs in cold temperatures,” he said.
When it comes to the number before the “W,” think “winter,” not “weight,” because that number on the left represents the oil’s maximum viscosity or flow at a low temperature. The lower the number, the better the truck will start in colder temperatures.
“An SAE 5W oil will perform better at low temperatures than a 10W or 15W,” Granger explained. “The five means it thickens at a lower rate in cold temperatures compared to a 10W or 15W. When an oil becomes thick in cold temperatures, it creates drag, so using a 5W-40 oil in cold climates is a good strategy, as the engine will start better in those colder temperatures.”
While some get hung up on the number on the left, Granger said the number people should really pay attention to is the one on the right.
“That’s the number that indicates the viscosity recommended by the OEM for the engine at normal operating temperatures, and is the real indicator of how well an oil will lubricate,” he said.
But, before you default to choosing an oil with a high number on the right, Leonard Badal Jr., Global Delo brand manager for Chevron, said lower viscosity oils can be the right choice for some vehicles.
“Higher viscosity oils are not necessarily always the best oils to select,” he said. “Lower viscosity oils can also provide excellent protection and performance especially for model-years 2012 or newer.”