The European Commission has proposed its first fuel economy target for heavy-duty vehicles, something that could be costly for heavy-duty original equipment manufacturers. The likes of Volvo, MAN and Scania will need to introduce new technology and improve engine efficiency to keep ahead of any punitive measures taken by European authorities enforcing fuel economy and emissions levels.

The commission will set an emissions reduction target of 15 percent by 2025 with a secondary goal of 30 percent in 2030 compared with 2019 levels. Transport accounts for almost 25 percent of the EUs yearly carbon dioxide emissions, with road vehicles making up around 70 percent of that.

Base Hit

Engine oil formulations have been shifting away from Group I base oils since the 1990s due to emissions regulations and other performance demands. Early air pollution regulations focused on smog, acid rain and nitrous oxides. Group II and III oils have less sulfur than Group I, so using Group II or III helped reduce sulfur oxide emissions and reduced levels of SAPS (sulfated ash, phosphorus and sulfur), which can foul filters installed to capture particulate matter.

Demands for longer drain intervals and improved engine cleanliness also encouraged replacement of Group I oils. Group II and III base oils have higher levels of saturates, which translates into greater oxidative and high-temperature stability, helping stave off oil deterioration and formation of deposits and sludge.

Group II and III both provide aid for all of these performance demands, though Group III oils tend to have even higher levels of saturates and the highest quality Group IIIs have lower sulfur levels. But with fuel economy, Group III generally has an advantage over Group II.

Lubricant formulators contribute to fuel economy by reducing the viscosity of their products, since thinner oils create less drag on moving engine components. Lower viscosity is most important at lower operating temperatures, where any particular oil is thickest, and where disproportionate amounts of fuel economy are lost. It is also important, though, for oil films at higher temperatures to remain thick enough to continue protecting engines.

This is where viscosity index comes in. V.I. measures an oils ability to maintain its viscosity across temperature ranges, and Group III oils by definition have higher V.I. than Group II, which are defined as having the same V.I. range as Group I. To date, passenger car engine oils have been asked to contribute more to fuel economy than heavy-duty oils, and as a result, 5W multigrades are not the predominant viscosity grades in developed markets, and 0W products are beginning to catch on, compared to 10W multigrades that prevailed 15 years ago. According to Amy Claxton, principal of U.S. consulting firm My Energy, top-tier 5W and 0W multigrade oils in developed markets can no longer be blended with Group I or standard Group II base stocks but require Group II+ (the highest quality Group IIs), Group III, polyalphaolefins or a combination thereof.

Trucking Along

Now that fuel economy demands are spreading to trucks, heavy-duty engine oils are also trending to 5W-30 formulations from the more traditional SAE 15W-40, 10W-40 and 10W-30 grades – at least in developed markets. Some go as far as to say SAE 5W-30 heavy-duty engine oil will command a 20 percent share of the European market in less than three years.

Some suppliers of Group III oils and say they are ideal for formulating 5W-30 heavy-duty engine oils given their lower cold cranking simulator viscosity and Noack volatility properties.

Additive packages for HD engine oils contain a lot more components which dont necessarily have good lower temperature performance. So in this case, Group III becomes an enabler to formulate at 5W-30, Nick Clague, SK Lubricants global technical manager, told LubesnGreases.

Ray Masson, managing director of petroleum products trading company Pumacrown, had a less definitive position. Both Group II and Group III base stocks are suited for the 5W-30 formulations that heavy-duty OEMs turn to to help lower emissions and reduce fuel consumption. Group III has an edge in low-SAPS lubricants but the difference compared with Group II+ is small. A choice between the two – Group II and Group III base stocks – at present simply means you have a lot of weighing up to do.

According to Masson, there are few if any technical constraints in making Group II base stocks as effective as Group III.

Clague, who is responsible for the technical management of SK Lubricants Yubase business, countered that the incentive to use Group III instead of Group II will grow as OEMs and fleet operators continue to seek fuel economy improvements.

One way to improve fuel economy via the base oil is to blend to a lower viscosity grade. This is where Group III base oils have an advantage over Group II in that they have lower volatility and better low-temperature properties.

It is because of the subpar low-temperature properties of the additive package that Clague considered it to be very unlikely that Group II will be used for these lower viscosity grades. Even 10W-30s in some formulations need a level of Group III as a trim stock to meet viscometric requirements, he explained.

That said, the choice between the two oils for Masson comes down to other limiting factors such as availability, a blenders operational capability and price.

The European market was originally dependent on Group I base stocks, and to lift these oils to a higher standard Group III base oils were employed, because these lubricants were available in Europe whilst Group II base oils were not. That has changed and will be changing even more so when the ExxonMobil operations in Rotterdam are up in 2019, he said.

The $1 billion project will begin supplying the European market with a rumored 900,000 to 1 million metric tons per year of Group II base stock from early 2019 onwards.

Flexible Market

Aftermarket refill recommendations are moving to lighter viscosity at a much slower pace than OEM factory fill oils. A source at one U.S. Group II supplier, who spoke on condition of anonymity, contended that replacement fill oils will continue to be in the SAE 10W to 15W range for many years to come, especially outside Europe and North America.

Clague sees a more dynamic market. If you look at the light-duty engine oil markets in Europe and the U.S., you will see that low-viscosity engine oils are being used at large rates for service fill. However, this has taken many years to achieve, and there is still growth potential in this market. The heavy-duty market is typically a few years behind the light-duty market in terms of viscosity grade transition, but in Europe nearly all heavy-duty OEMs are now using 5W-30 or lower for their factory fill.

If anything, Clague says, you could argue that without Group III base oils this transition [to lighter viscosity grades] would have been much slower, as it is difficult to formulate to these lighter viscosity grades with Group II base oils. This doesnt mean there isnt a place for Group II in the European market, but it is not likely for low viscosity grade engine oils.

But, as the U.S. source points out, even if heavy-duty formulations open the door to the use of Group III base oils, one must remember that heavy-duty OEMs place a premium on reliability given the higher loads. As such, they are more cautious.

Indeed, with nearly half of global base stock demand in industrial and process oils, which are not moving to lower viscosity oils, there will be continued need for grades produced in Group II plants.

Group II plants have more flexibility than Group III plants in the properties of the oil that they make. Today, the feedstock for most Group III plants is unconverted bottoms from fuels hydrocrackers. Since the feed is already hydrocracked, the main task of the base oil plant is just to dewax, and the viscosity index of the base oil is essentially set.

Most Group II plants have their own hydrocracker, so they have flexibility to crack more severely, which reduces yield but can raise V.I. to Group III levels.

When specifications change, Group II producers are better equipped to move in tandem with those changes. They can move from Group II to Group II+ to Group III as the market dictates, the source continued.

However, Clague maintains that it is possible to produce Group III in a consistent way. When base oil plants are built, they are built to produce a quality of base oils be it Group I, II or III. A Group II plant is built around the economics of making Group II base oils. These plants are capable of also producing Group II at a higher V.I. or Group III but with the expected yield losses from changing production it might not necessarily be economically viable, especially if the same feedstocks that are used to make Group II will be used to make Group III.