It will also spur additive suppliers to develop optimized low-SAPS additive systems to deliver the required balance of fuel economy, engine protection and reduced emissions. Calder identified these three parameters as the drivers having the biggest impact on the lubricants industry today and into the future.

What OEMs Want

Calder summed up current original equipment manufacturer requirements for todays passenger car motor oils as 20,000 to 30,000-kilometer drain intervals, excellent wear protection, engine cleanliness, compatibility with exhaust aftertreatment devices and fuel economy. While these needs are being met by SAE 5W-30 viscosity grades, in the future OEMs will place far more severe constraints on passenger car engine oils.

They will want to preserve existing drain intervals, wear protection and engine cleanliness, he said, even when running on biofuels.

In addition, oils will have to deliver significantly improved fuel economy while maintaining compatibility with exhaust aftertreatment devices. Calder contended that these requirements will necessitate a move to SAE 5W-20 or SAE 0W-20 viscosity grade oils, formulated with additives that have minimal amounts of sulfated ash, phosphorus and sulfur – collectively referred to as SAPS.

Durability is a critical factor because OEMs are downsizing engines and turbocharging them to maintain power output. Were also seeing more biofuel in the market, said Calder, and all of those things are putting more stress on the engine and on the lubricant. Therefore, we really have to focus on lubricants to ensure that they deliver the durability required.

Engines are getting smaller, and one of the consequences is a need for increased wear protection. More torque from a downsized engine means higher loads on smaller bearings, said Calder. This is a challenge to the lubricant film strength, increasing the possibility for higher wear. Lubrizol estimates that a 10 percent increase in output torque increases bearing stress by 39 percent.

Another factor to consider is that more engines are being turbocharged to maintain power output. Turbocharging can increase the severity of the stress placed on the lubricant, Calder said. A critical area is the turbocharger bearing. Some of the failures we see in turbochargers are bearing seizure and turboshaft failure.

In addition, turbocharging can lead to increased oxidation and oil degradation, resulting in deposits that block critical engine passages. In addition, the increased use of biofuels can have a significant effect on lubricant performance. Calder cautioned that biofuels will continue to be a significant part of the fuel pool. If the lubricant becomes highly diluted by biofuel, sludge, oxidation and piston deposits can increase significantly. Its clear from our research, though, that the quality of the lubricant can have an impact in preventing these problems, he said.

OEMs have addressed their concerns about biofuels in recent and forthcoming specification changes by building in biofuel protection. For example, Calder said, the most recent ACEA specifications include some biofuel tests to ensure that protection is built in. That will continue into the future. For example, future ACEA passenger car specifications are likely to include the MB OM646 BIO, MB M271 EVO and PSA DV6 tests to address biofuel concerns.

Cutting Emissions

Calder then reviewed the history of European emissions standards, showing how they have evolved over the years. Since the Euro standards were introduced in 1991, allowable nitrous oxides from gasoline and diesel engines have dropped steadily. We are now dealing with Euro 5 standards, which significantly reduce particulate matter emissions from passenger car diesel engines, he said.

What I really want to highlight is there was a step change in the industry with the introduction of the Euro 4 standard in 2005 when we saw the widespread use of exhaust aftertreatment devices such as diesel particulate filters. This led to the development of low-SAPS lubricants. Today, further investment in low-SAPS oils is required as exhaust restrictions become more stringent.

Another clear message from OEMs and government regulators is that carbon dioxide reduction targets are important across the globe. In Europe, OEMs appear to be on target to meet the limit of 130 grams per kilometer of CO2 emissions for all of their vehicles by 2015, Calder said. Their focus now is on the 2020 target of 95 g/km.

Improving Fuel Economy

Calder said, Fuel economy targets have been built into lubricant formulations for many years. There has been a clear shift toward thinner SAE 0W-20 and SAE 5W-20 oils in this regard because these oils not only improve fuel economy but also help reduce CO2 emissions.

The question is, can the lubricant continue to deliver more fuel economy and how much? He then reviewed the typical fuel economy levels produced by different viscosity oils currently available in the marketplace. He showed that a typical ACEA C3 5W-30 oil will on average improve fuel economy by 2 percent compared to a conventional oil, while a typical ACEA C2 5W-30 yields a 2.7 percent improvement. Based on work Lubrizol has done with 0W-20 oils, we expect to see an average fuel economy rating of about 4 percent. So the size of the prize is potentially significant.

Calder cautioned, however, that it is important to remember that it is not just a case of taking existing technology and dropping it into an SAE 0W-20 formulation to get the maximum fuel economy. We added our current low-SAPS technology to an SAE 0W-20 oil and achieved a fuel economy improvement of about 3.5 percent. However, when we optimized the technology and reformulated the additive package, we delivered significant improvements in fuel economy performance from that oil.

Of course, fuel economy cannot be considered in isolation. We also have to look at durability, he said. Our testing of the optimized additive technology in the VW TDI engine test showed improved piston cleanliness.

Another area to consider is wear. Calder noted that as we use thinner oils, were going to get into lubrication regimes where wear will become more of a concern. More boundary lubrication occurs with lower viscosity oil, increasing the potential for higher levels of wear. There are things we can do to change that, Calder said. For instance, advanced detergents, dispersants and inhibitor packages are being investigated that can move the lubrication regime back into the hydrodynamic region, improving wear performance.

Base Oil Impact

Lubrizol carried out extensive work to model the effects of using lower viscosity base oils. It developed models that compared different combinations of base oils, viscosity modifiers, additive packages and components. We derived models from the test matrix to predict the physical characteristics of oils, including kinematic viscosity, cold cranking viscosity, high-temperature high-shear (HTHS) viscosity and Noack volatility, Calder explained. The aim was to understand the formulating window in which we have to operate.

In the first model, Lubrizol studied a baseline formulation of API Group III base oil with a low-SAPS additive package and high-performance viscosity modifier, designed to meet OEM engine performance targets. Formulators then plotted HTHS viscosity vs. Noack volatility or cold cranking viscosity.

With no viscosity constraints, a huge formulation window is possible. However, if the same formulation is limited to a viscosity of SAE 5W-20 and a Noack volatility of less than 13 percent, the formulation window shrinks significantly. And if viscosity is limited to SAE 0W-20 with a typical OEM-specified Noack volatility of less than 11 percent, the formulation window closes completely.

To reopen the formulation window, we had to use higher viscosity index base oils, said Calder. For example, we used PAO to reopen the formulating window somewhat. More work will be required to fully optimize the base oil contribution.

Calder summed up by saying, New engine technologies and more severe operating environments will require the development of new engine lubricants. This trend will drive increased demand for high quality base oils formulated with optimized low-SAPS additive systems to deliver the balance of fuel economy and engine protection required OEMs want.