Maintenance Q&A
Oil confusion and rough rides

By Paul Abelson, Senior technical consultant

I am totally confused by the new oils. I’ve been told they are OK to use like the old oil and also that they should only be used in new motors.

I have a 2009 Mack with a 450-horsepower MP8 motor that a friend drives for me. I drive my 2013 Mack Titan with the 605-hp motor. We also use our oil on our Dodge diesel pickup (Cummins) and our family cars (gasoline) so we can save shipping and storage.

My questions are: What should I use? Do I need to start buying a new oil? If so, which one? And why do we need two new oils anyway?

In your case, you can simply convert to the new API (American Petroleum Institute) classification CK-4. It is completely compatible with the CJ-4 used previously, just as CJ-4 replaced previous grades of oil. You may even want to change viscosities to see if you can improve fuel mileage and decrease wear.

Most wear occurs on start-up, as oil – especially when cold – starts to be pumped into the engine while the engine is turning and parts are rubbing together. The lower viscosity oils, SAE 10W-30 and fully synthetic SAE 5W-30 and 5W-40 allow these thinner-when-cold oils to be pumped more easily to quickly build oil pressure.

If you do change viscosity, check with Mack to make sure any remaining warranty on your trucks is not affected.

The other new oil, FA-4, may have some limited backward compatibility, but it’s primarily considered the oil for the 2017 fuel-efficient trucks and beyond.

When the EPA set out to reduce greenhouse gases (GHG), primarily carbon dioxide (CO2), they determined that the easiest and most effective way was to burn less fuel. This time, it’s not just engines that bear the task of meeting new standards. Tractor and trailer aerodynamics, tire rolling resistance, weight reduction and drive train improvements all play a part, along with engine efficiency. Three decades ago, the rule of thumb was one-third of fuel burned was lost as heat through the cooling system or out the exhaust; one-third was lost to internal friction and rolling resistance; and one-third went to actually powering the truck down the road. Today, we are approaching 50 percent for propulsion, and engineers expect to exceed that soon.

In practical terms, a few years ago 6 mpg was a dream. Today 8 mpg is reality and, with 10 mpg for everyone as a goal, most experimental trucks are topping 13 mpg.

The 2017 and future engines incorporate new technology to burn fuel more efficiently and lower internal friction. The new fuel-efficient oil, FA-4, is designed to work in these engines, especially at lower viscosities. When buying a new truck, find out what the factory fill is and stick with it.

As for your other vehicles, you can safely stay with CK-4 as long as your oil brand is gasoline compatible.

I own a 2010 Freightliner with just over 550,000 miles on it. I bought it new. It’s my fourth truck, so I know how to care for it.

This winter my ride quality started going south. I took it to my dealer. They checked the ride height first to see if it got knocked out of adjustment. It was OK. Then they checked the air bags for leaks and tears. Also OK. Next they checked the shocks. They were leaking oil, so the dealer replaced them and said that they would fix it. It did a little, but the ride is still bumpy. What can I do to get back my old ride?

Ride problems are often complex to diagnose and repair because they involve so many components that must work in harmony. The dealer was right to start with ride height, the easiest problem to diagnose and fix. The saying is to start with the low-hanging fruit. Leaking oil on the shocks was also an obvious sign. A properly working shock will have some oil misting on the inner tube, but leaking is more obvious. It’s a definite sign the shock is worn out. They were probably overdue for replacement, but one should never assume in truck maintenance.

The shocks may have worn out because of repeated impacts with poor roads and potholes, and that may have caused collateral damage to other components and fittings. These should be checked at least weekly, especially during winter. First, be sure all air lines to the suspension are clear of air bags. Check that nothing is chafing the rubber. Air bag bases are subject to damage from vibration and corrosion, as are air lines and fittings.

The Technology and Maintenance Council (TMC) has two Recommended Practices you should be sure your technician is familiar with before doing any work on your suspension: RP643A, Air Ride Suspension Maintenance, and RP648, Troubleshooting Ride Complaints. The latter is a 58-page document that lists all ride problems. It provides a systematic checklist for each one, and a set of procedures to follow to correct it. Several pages are devoted to your complaint of a harsh ride.

Because your suspension works on compressed air, it’s important to have an adequate supply. In winter, drain and “spitter” valves can freeze, leaving excess water in air tanks. If the water freezes in the tanks, it can reduce the usable air volume. This could cause a shortage of air to your suspension, especially after repeated heavy braking. It’s a good idea to take steps to keep your compressed air dry. Change desiccant cartridges on schedule and be sure all drain valves work. Drain the tanks daily. LL

(Editor's note: When sending in questions for Maintenance Q&A, please include the make and model of your truck and your vehicle identification number (VIN) as well as your contact information. Paul Abelson tries to respond to every question, whether it's published or not. Send questions to