It is no secret that China has some severe air quality issues to contend with, and the Chinese government is serious about tackling them. Among a range of recently introduced air quality improvement measures are some tough new standards for vehicle emissions. Known as China 6, the legislation will come into effect in July 2020, and its impact cannot be understated. It will represent one of the most significant events in the history of passenger car engine oils in the worlds largest automotive market.

And it will not end there. Further tightening of the legislation and the introduction of real driving emissions tests will arrive in 2023, making China 6 the worlds strictest emissions legislation (Figure 1).

This is all occurring at a time when turbocharged gasoline direct injection engines, with their added durability challenges, are powering most of the cars sold in China, in parallel with ever-tightening fuel economy limits imposed by the government. The simultaneous collision of these factors will have a big impact on the global engine oil marketplace.

Testing for Necessary Performance

Particulate matter emission limits applied to all engine types will result in widespread adoption of gasoline particulate filters, driving the need for engine oils with lower levels of sulfated ash, phosphorous and sulfur, known as SAPS. Downsized TGDI engines will require enhanced deposit and sludge protection. Low viscosities and fuel-efficient additive technologies will be required to ensure original equipment manufacturers can comply with reduced fuel consumption limits.

A key part of the process to develop solutions for Chinas engine oils for several years has been the use by additive companies of carefully controlled long-term field trials to produce highly realistic evaluation of potential solutions. The belief is that accelerated testing, with conditions or fluids artificially modified for increased severity, is an important baseline in engine oil development. But there is no substitute for real-world proof of performance obtained under Chinas unique operating conditions.

Lubrizol has performed three major field trials that focus on durability, fuel economy and emissions. The first trial showed that the basic engine oil technology widely used in China at the time was incapable of protecting TGDI-powered cars when running on poor quality fuel. Engine oils meeting the European Automobile Manufacturers Associations ACEA C specification – for gasoline- and diesel-powered light-duty vehicles with exhaust aftertreatment systems that contain catalysts – provided much better protection against damaging deposits and sludge.

A second trial evaluated fuel economy and wear, showing that SAE 0W-20 versions of these formulations were very capable of combining reduced fuel consumption with excellent wear protection (Figure 2).

The most recent field trial carried out over 160,000 kilometers on a fleet of nine vehicles in Shanghai evaluated engine oil effects on gas particulate filters. The trial clearly demonstrated that higher ash oils produce a much greater increase in exhaust backpressure, with the potential to affect engine performance and durability. It has been shown that some ash can be beneficial, as the ash cake actually improves the filtration of soot particles.

While this is true, the field trial data demonstrated that it requires relatively little ash and a short duration to achieve this improvement, and the filter blocking effect of higher-ash oils is a major risk for the end user. The 0.79 percent ash ACEA C oil was actually better at reducing the particulate number while at the same time limiting filter blocking (Figure 3).

The same trial also included the monitoring of low-speed pre-ignition, an increasingly important aspect of lubricant performance and now recognized as a key durability parameter. An ACEA C specification technology, at SAE 0W-20 viscosity and 0.8 percent sulfated ash, was formulated specifically to reduce LSPI, and this can be seen in the results from the trial (Figure 4).

As a result of our testing, the implications are clear: To meet the requirements laid out in China 6, a significant step up in the quality and performance of engine oil technology used in the field will be required.

Whats Next?

It is expected that the ACEA sequences will include an LSPI requirement in the next update, due in late 2019. Many OEMs are now also considering LSPI durability when specifying engine oils, as some oils show good LSPI prevention when fresh but quickly lose that property due to the rapid depletion of chemistry involved. LSPI protection needs to be maintained throughout the life of the engine oil.

Additionally, while the work performed by Lubrizol was designed specifically for the Chinese market, the results are applicable elsewhere, too. The next major market to adopt similar legislation to China 6 will be India, with its forthcoming Bharat 6 emissions regulations. The Indian government plans to implement Bharat 6 in a similar timeframe to China 6 – April 2020 for stage 1, with full implementation arriving in April 2023.

Requirements in Europe will closely mirror China 6, and though the scope of the application is a little different, the principles remain the same, such as the issues of ash loading of the filter with backpressure and engine performance consequences. However, Euro 6 particulate limits currently apply to diesel and gasoline direct injection engines but not port fuel-injected gasoline engines. Lubrizol has previously done dynamometer-based research in partnership with a European OEM to understand the benefits of mid-SAPS engine oil technology. The work in China was a follow-on from this research to get real fleet test results on Chinas roads.

China 6 legislation is based on Euro 6, which is already in place. Therefore the challenges with real drive emissions and particulates are similar. Europe is a little ahead of China in GPF adoption, and OEMs in Europe are generally relying on ACEA C as the foundation for GPF-compatible lubricant specifications.

Chinas passenger cars have improved dramatically in quality over recent years and can now compete with the best models from established global OEMs. Modern engine hardware needs the right oil to ensure clean, reliable and fuel-efficient operation during many years of service. High performance, aftertreatment-compatible technology has been shown to provide the ultimate in protection and efficiency, enabling low emissions and reduced fuel consumption over a long, reliable engine lifetime.