For at least a decade, Europes vehicle manufacturers maintained separate classes of engine oils to service their light vehicles – A for gasoline engines and B for light-duty diesel engines. In November, however, two major changes were launched for these oils.

First, the two existing classes were combined into a single new ACEA Oil Sequence – A/B – covering both types of engines. This move allowed ACEA to reduce the number of active categories to just four.

The second major change, equally consequential, was the introduction of a new Sequence class, C, for light-duty engines with aftertreatment devices. There is no counterpart to this category in the United States and none is currently contemplated.

Why did Europes vehicle manufacturers combine the A and B classes? There were three principal drivers, explained Carl Stow of Ford UK, spokesman for ACEAs light-duty lubricants working group. First, reducing the number of separate categories. Second, a concern that some B oils lacked full robustness. And third, to make certain that each class of engines would be lubricated by an oil specifically targeted to this class.

In early 2004, Europe had nine separate, active light-duty engine oil categories crowding the shelves – A1, A2, A3, A5, B1, B2, B3, B4, B5 – each targeted at a specific engine configuration. (North America by contrast had just two, API Service Category SL andILSAC GF-3.)

Nine was just too many categories, Stow said bluntly. Some were unnecessary and they created confusion. We reduced the number to four without any loss of protection.

He also noted, There was a concern that some B category oils were not being evaluated effectively for certain parameters, for example, oxidation stability. So if the oil did not claim an A rating, it was possible that it might not have adequate robustness and be able to protect the full fleet. So we merged the two categories to make sure that all light-duty vehicles were protected. In point of fact, most light-duty oils had both an A and B rating so there was not a whole lot of extra testing to do.

As for backward compatibility, Stow is satisfied. Our A and B legacy categories are fully covered by the 2004 merged A/B categories, with full backward compatibility, he stated.

Consumer Choice

How do consumers make a choice of an oil among the several available categories? The ACEA system lets drivers select from several tiers of quality and drain interval options (see chart, page 10).

An A1/B1 oil is a relatively inexpensive but very fuel-efficient, good quality oil formulated with mostly Group III base oil which can protect an engine for up to 12,000 miles, Stow said. A3/B3 oils have about the same performance level as A1/B1 but with less focus on fuel economy. A3/B4 are similar to A1/B1 but with more of a synthetic base oil content.

A5/B5 are called top tier. They contain all Group III or Group IV base oils and are the highest priced oils. They provide gasoline and light-duty diesel engines with up to 20,000 miles of protection.

European emission requirements today are driving much that has to do with engine oil specifications; theres little question on that proposition. Meeting emissions requirements is a legislative duty and of course the top priority, stated Stow. But in addition, we are continually building engines with ever-higher performance and the oil quality needs to go up to support that requirement, too. Emissions, fuel economy and long drain intervals, as well as higher performance engines all have to be balanced. Thats why the minimum base oil quality were demanding in Europe is predominately Group III and above.

Undergoing a C Change

ACEA represents vehicle manufacturers, and tightening emission limits of course are reflected in its Oil Sequence development efforts. About two years ago, the lubricants working groups within ACEA began focusing on the new engine technology scheduled to be introduced in 2006 to meet Euro 4 emissions requirements.

Stow pointed out, We were concerned about the effect of lubricants on aftertreatment systems, especially diesel particulate filters (DPF), which are particularly sensitive to ash depositions and catalyst blocking. Throughout our discussions and from the beginning, we kept up a continuous interaction with the oil and chemical additives industry on formulation and performance requirements and what we saw as the chemical elements. We solicited, and carefully considered, their input all along the way.

What it came down to, he continued, was a concern with three things; what we call in a shorthand way SAPS – sulfated ash, phosphorus and sulfur. Each of these engine oil components can have a negative impact on an aftertreatment device.

Concern with SAPS is not new in Europe, or North America. The catalyst poisoning effect of phosphorus, for example, has resulted in this reliable and inexpensive wear control agent being reduced, from 0.12 percent mass in engine oil formulations 10 years ago, to 0.08 percent in the ILSAC GF-4 engine oils specified now by North American automakers. Even lower phosphorus levels are likely for GF-5. And in APIs new diesel engine oil upgrade, called PC-10, now under intensive development, SAPS is considered a chemical box and limits for each of the offending components have already been agreed upon.

In Europe, the auto industrys deliberations resulted in the establishment of a new ACEA Oil Sequence, C, for Catalyst Compatibility Oils. It is roughly based on the top-tier A5/B5 oil category, with additional safeguards for emissions control systems. C includes three categories of oil – C1, C2 and C3 – each of which, said Stow, reflects and responds to the needs of either a single or group of different OEMs. Three classes, three different needs, roughly reflecting the different stages of OEMs in their aftertreatment approach and progress.

Although the base engine performance of each of the three classes is pretty much the same, we simply were unable to compromise down to a single specification, Stow explained. Hence, the three classes. For example, C1 has a maximum phosphorus level of 0.05 percent, which is very low, while C2 and C3 each have limits of 0.07 to 0.09 percent. Some OEMs were cautious about a 0.05 percent level and so they have the option of C2 or C3.

Competitive Edges

Stow made a revealing point. Theres a wide variety of data availability among individual OEMs, he remarked. Those OEMs with a lot of data were entirely content with the SAPS limits. Other OEMs, however, had less data and their comfort level was not as high. Were very competitive here and that includes providing information on how much testing weve done and the quantity of data weve obtained. So while some firms had developed considerable data, they were reluctant to share it.

In Europe, a lot of commercial owners have both light- and heavy-duty vehicles in their fleets, and they want the flexibility of an oil that can lubricate both engine classes, Stow said. In the past there were, in fact, oils that could meet the B (light-duty diesel) and E (heavy-duty diesel) categories.

However, said Stow, the engines that we are developing, higher in power and with new aftertreatment devices, need a specific oil. If the technology calls for an A/B or C oil, thats what should go into that engine. Oil companies, however, didnt see eye-to-eye with us on that point. They preferred the flexibility of a single fleet oil. Thats not possible now because the E category oils are significantly different, technically, from an A/B or C category oil, with entirely different tests and little likelihood for an oil to meet the specifications of both categories.

So are the C oils backward compatible for servicing older engines? No, replied Stow. We are not confident yet that these oils are backward compatible. But within a couple of years well have a better view. Some vehicle trials will have to be done on older vehicles. And well have to work very closely with oil and chemical additive companies so that [by 2008] well be able to obsolete older oils and ensure they are replaced with oils that are backward compatible.

Final Thoughts

The establishment of three distinct C classes to accommodate individual auto companies or groups of companies starkly illustrates the difference between the North American and European oil quality systems. The former cannot incorporate these kinds of individual OEM requirements or technical distinctions; hence, ongoing compromise to meet all OEM requirements results in a North American classification system that continually tends toward a lowest common denominator oil.

Another difference is that the new C Sequence was completed not in a nail-biting cliffhanger – as North Americans resignedly have come to expect – but smoothly ahead of time. Setting up a European catalyst compatibility category in 2004, although this oil will not be needed until 2006 at the earliest, was forward-looking and allows oil companies to be ready then.

We are confident, Stow said in closing, that these oils will be available for OEM dealerships for warranty servicing beginning in 2006. The big test will come starting in 2008 when cars begin to go out of warranty and are serviced by non-dealers. Whether non-dealers will be able to find shelf space for all the oil needed then, including these essentially niche products, will be the test.