Not all 10W-30 engine oils are created equally

Not all 10W-30 engine oils are created equally

Vehicle manufacturers and many fleets are moving to lower viscosity oils to obtain better fuel economy and help reduce greenhouse gases compared to SAE 15W-40 engine oils.


Vehicle manufacturers and many fleets are moving to lower viscosity oils to obtain better fuel economy and help reduce greenhouse gases compared to SAE 15W-40 engine oils. High-quality, low-viscosity oils can provide between 1% and 3% increase in fuel economy.

Even the smallest increases in fuel economy can result in significant reductions in fuel consumption and carbon dioxide emissions. For example, every U.S. truck increasing its fuel economy by just 1% would see an annual reduction of over four million tons of carbon dioxide emissions, which is the equivalent of removing more than 20,000 trucks from the road.

Lower viscosity oils pump more easily and help to reduce engine friction, which can improve fuel economy. There are different types of viscosity measurements that can be used to describe and measure the viscosity. One such method is called the high-temperature, high-shear (HTHS) viscosity (defined as an oil’s resistance to flow under high-stress conditions at operating temperatures) that distinguishes CK-4 oils from FA-4 oils for modern engines. HTHS is seen as a more accurate method for measuring viscosity. 

The stated viscosity of an oil does not represent an exact viscosity, but rather a viscosity within a range on the Society of Automotive Engineers (SAE) viscosity scale. SAE engine oil viscosity is measured in centistokes (cST) at 100°C. “W’ grades, or the number before the “W” in the SAE viscosity, are measured at 40°C. For example, 10W-30 engine oils can fit anywhere in the range of 9.30 cST to 12.49 cST. Engine oils closer to 9.30 cST will provide better fuel economy benefits than oils closer to 12.49 cST. Therefore, you could have two separate 10W-30 engine oils produce two different results in fuel economy.

SAE oil viscosity grades are defined by four different tests. Low-temperature pumping and cranking viscosities define the winter grade (for example, the 15 in 15W-40). HTHS dynamic viscosity contributes to the SAE viscosity grade definition (for example, the 40 in 15W-40). Low shear kinematic viscosity (KV100) contributes to the definition of monograde oils and provides a viscosity range for high-temperature viscosity grades in multigrade oils.

The stated viscosity of an oil does not represent an exact viscosity, but rather a viscosity within a range on the Society of Automotive Engineers (SAE) viscosity scale.

Switching to a lower viscosity grade SAE oil, for example, from a 10W-40 to a 10W‑30 oil, will provide modest fuel economy benefits. Even within a viscosity grade, differences in HTHS viscosity could affect fuel economy. 

The minimum HTHS viscosity for (XX) W-30 CK-4 oils is 3.5 centipoise (cP). FA-4 XXW-30 oils have HTHS viscosities between 2.9 and 3.2 cP, which help to enhance fuel efficiency further. They are designed to provide fuel economy without sacrificing engine protection in a range of applications. 

For example, for a specific heavy-duty engine, switching from a 15W-40 CK-4 oil with a 3.9 cP HTHS viscosity to a 10W-30 oil with a FA-4 (2.9 cP) HTHS viscosity provides a fuel economy improvement of about 1% in high-speed, high-load driving conditions and up to four percent at low-speed, low-load driving conditions. 

Manufacturers are using this information to design modern engines to improve fuel economy and fleets should considering moving to low viscosity oils such as SAE 10W-30. Both low viscosity CK-4 and FA-4 oils will provide long oil life and the same strong level of engine protection with FA-4 oils specifically intended to deliver additional fuel economy benefits for modern diesel engine technology over API CK-4 oils. Always follow original equipment manufacturer recommendations as some OEMs do not yet allow the use of FA-4 oils.

Dan Arcy is the global OEM technical manager for Shell Lubricants.

Check out the rest of the June digital edition of Fleet Equipment here.

You May Also Like

PACCAR Parts names Weller as 2023 Supplier of the Year

Throughout 2023, Weller contributed to PACCAR Parts overall network performance by exceeding 17% y/y growth.


PACCAR Parts named Weller Truck Parts as its 2023 Supplier of the Year, recognizing the supplier that the company says demonstrated outstanding operational achievements, sales growth, parts availability, and program support last year.

Over the course of 2023, PACCAR Parts says Weller contributed to its overall network performance by exceeding 17% year over year in growth. The company adds that Weller produced an on-time shipping rate of more than 99%.

Freightliner M2, SD Plus Series launch updates its medium-duty truck offering

Freightliner introduced the new Plus Series–enhanced versions of its M2 and SD models, including the M2 106 Plus, M2 112 Plus, 108SD Plus, and 114SD Plus. The enhanced models provide a major update to the interior and electrical systems of the M2 and SD models. The OEM noted that the Plus Series is designed to

Truck cruise control technology that looks at the road ahead

If you’ve ever visited the Northeast region of the country, you’ve most likely encountered intimidating terrain. The winding roads. The steep hills. The intricate routes that challenge any seasoned driver, and, most recently, advanced cruise control systems that aim to improve fuel efficiency and driver comfort.   Related Articles – Four ways A.I. can help cut

Four ways A.I. can help cut diesel fuel costs

The fluctuation of fuel prices has made it more challenging to operate day-to-day. Drivers get paid by the mile, and, when fuel costs go up, margins shrink, impacting how fleets profit and pay their employees. Intelligent technology can lessen the impact of high prices by improving overall fuel efficiency. Related Articles – New ways to

Peterbilt GM Jason Skoog charts today’s truck support, tomorrow’s truck solutions

Peterbilt made headlines recently when it became the first major North American OEM to open orders for an electric truck, the Peterbilt 220EV. In this exclusive interview, Peterbilt General Manager and PACCAR Vice President Jason Skoog details the technology investments that are keeping fleets productive during this year’s trying pandemic and laying the groundwork for

Peterbilt General Manager PACCAR Technology Electric Truck

Other Posts

Clore Automotive appoints new vice president of sales

The company says his invaluable experience and customer-centric approach make Dan Lucas right for the role.

Continental Tire opens Retread Solutions Center in South Carolina

The company hopes to uncover new improvements and technologies to innovate the retread process.

Dayton Parts introduces fuel injector wiring harnesses, EGR coolers, trailer air tank reservoirs

Fuel injector wiring harnesses, exhaust gas recirculation coolers and trailer air tank reservoirs designed to match OEM spec.

Thermo King launches Electrification Readiness Program

The dealer program is designed to enable customers’ transition to more sustainable fleet solutions, improved efficiency and decarbonization.