On December 1, 2016, new diesel engine oils — API CK-4 and FA-4 — became available for purchase.
The new oils were developed in response to changes in engines necessitated by engine emissions regulations. Engine oils will play a role in meeting those emissions regulations because of their lower viscosity.
As a refresher, viscosity is the measure of a fluid’s internal resistance to flow. In a truck’s engine, mechanical losses from pumping and friction consume approximately 16% of the total energy input to a vehicle. Lower viscosity oils will reduce those engine mechanical losses, thereby reducing fuel use.
Our Confidence Report on Low Viscosity Lubes found that Class 8 over-the-road fleets can realistically expect fuel savings in the range of 0.5% to 1.5% switching from a 15W-40 engine oil to a 5W-30 or 10W-30 one. This is true whether you are using the now old CJ-4 oil or the new CK-4 oil.
Some people erroneously believe that heavier engine oils provide better engine protection and therefore increase engine durability. But remember before engine oil can be released into the market it must the durability requirements of every major OEM. All major North American engine OEMs have approved lower viscosity oils for over-the-road applications.
So what does that mean? Basically it means you should have no concern switching to a lower viscosity oil in over-the-road applications.
Because two new oil categories arose out of the PC-11 category there is some confusion about which oil fleets should use. The new CK-4 oils even in their low viscosity formulations can be used in place of CJ-4 oils. In fact they are approved for engines going back to model year 2010
The jury is still out on the backward compatibility of FA-4 oils, which we believe will offer an additional 0.4% to 0.7% fuel economy improvement when switching from CJ-4 or CK-4 5W-30 or 10W-30 oils. Each OEM is addressing this issue and will announce their recommendations.
Low viscosity lubes have been on the market for many years, the development and release of a new engine oils has just brought more attention to them. And from what we see switching to a low viscosity lube is a no brainer. So just do it.