About 40% of the largest, most efficiency-conscious North American fleets have switched to lower-viscosity engine oils, but their industry-wide adoption lags at about 20%. A new Confidence Report from the North American Council for Freight Efficiency (NACFE) makes a the case for switching to lighter-weight engine oils.

NACFE found through its study that fleets can expect fuel savings in the range of 0.5%-1.5% when switching from a 15W-40 to thinner viscosity 5W-30 and 10W-30 oils. When a new FA-4 engine oil category is launched in December 2016, a further fuel savings of about 0.4%-0.7% will be attainable, NACFE reports.

“The arrival of new categories of engine oils will help raise awareness of the fuel efficiency benefits of the large range of oils available,” said Mike Roeth, operation lead, Trucking Efficiency.

Study manager Yunsu Park, said the fuel savings achieved through the use of lighter-weight oils are real.

“Lower viscosity engine oils deliver fuel savings, and concerns over lower engine protection are simply not valid anymore,” Park said.

The fuel savings attainable by switching to a lower viscosity oil are, however, difficult to measure in a fleet environment. So NACFE suggests fleets base their decisions on an expectation they’ll see a 0.5% fuel economy improvement.

“If an acceptable return on investment is shown with this low level of fuel savings, fleets should be able to confidently make the switch,” NACFE reports.

Misperceptions about lighter-weight oil have hindered its more wide-scale adoption. NACFE reports there was a belief within the industry that heavier oils provide better engine protection and increase engine durability. However, that myth has been debunked through comprehensive testing. Fleets should, however, only used OEM-approved oils.

“Given the importance and the complexity of an engine oil’s performance and function, approval and release of new oils into the market is not taken lightly,” NACFE wrote in its report.

Some fleets using lower-viscosity engine oils have been able to also extend drain intervals, which can help offset the price increase. One fleet involved in the study said it extended its drain intervals by 20,000 miles when switching to lower-viscosity engine oil.

A challenge to the more widespread adoption of lighter-weight oils is the cost. It could cost as much as 30-40% more to make the switch from a mineral-based 15W-40 to a synthetic or semi-synthetic lower-viscosity oil, NACFE warns. Another issue to consider is compatibility within a fleet. Most 5W/10W-30 oils available today are compatible with engines dating back to at least 2010.

NACFE also noted fleets will soon be faced with more choices when it comes to engine oil, thanks to the introduction of the new FA-4/CK-4 category oils set to be launched in December. CK-4 will be a straight replacement to today’s CJ-4 oils while FA-4 will offer greater fuel economy but questions remain about compatibility of pre-2017 model year engines. It will be up to the engine manufacturers to decide to what extent, if any, they’ll allow FA-4 in their older engines.

For now, NACFE says it’s “highly confident” that fleets should consider the move from 15W-40 oils to ones with lower-viscosity, in consultation with suppliers. You can find the complete report on TruckingEfficiency.org.