In the past, said McMillan, automotive engine oil performance was perceived as relying primarily on additive performance. Base oil performance was considered minor.

If you had wear or oxidation problems, you added more ZDDP [zinc dialkyldithiophosphate]; for deposits, more deposit inhibitors; for pumpability, more pour point depressants; for fuel economy, more friction modifiers; and for foam, more silicone.

But today were living in a world of tradeoffs, McMillan said, citing the tradeoffs between high phosphorus and catalyst performance, between high viscosity and fuel economy, and between deposit control/detergent level and fuel economy. Additive performance alone is not enough. The need for optimized oil performance includes both base oils and additives.

ILSAC – the group representing U.S. and Japanese automakers in the development of engine oil specifications – wants improvements in volatility control, oxidation stability, low-temperature viscosity both for pumping and starting, and both initial and retained fuel economy.

McMillan, who is based in Washington, Mich., pointed to three factors driving the need for improved engine oil performance: greater use of spark-ignited direct-injection and turbocharged engines; sludge problems experienced in the field by some automakers; and the move by General Motors in particular to extend engine oil-change intervals.

The sales-weighted average oil drain interval for 2005 model year GM vehicles equipped with the Engine Oil Life System, the onboard computer algorithm that tells drivers when its time to change the oil, is 8,500 miles, said McMillan. The typical oil drain interval specified by GMs competitors is 5,000 miles.

Approximately 5 million GM vehicles with EOLS were produced in the 2005 model year, and the system saves one oil change per year, McMillan told Lube Report. The typical volume of oil per change is about 1.3 gallons, and the typical cost is about $30. Thus EOLS will save some 6.6 gallons of oil annually for the 2005 model year fleet, and will save the drivers about $145 milliona yeardue to reduced oil changes. And General Motors expects major improvements in oil drain intervals in the near future. Thirty thousand mile intervals will be possible with just minor engine modifications and appropriate oil technology.

Base oils will play a key role in the meeting the next generation of engine oil specs, dubbed GF-5 and scheduled for commercialization in 2009. Compared to Group I, said McMillan, Group II, II-plus and III oils are known to provide fuel economy benefits, and better oxidation stability helps retention.

In addition, their good volatility performance will help control oil consumption and protect emissions systems. Another goal is to someday allow blending of 0W multigrade oils without having to use Group IV base stocks, although Group IIIs arent there yet. Other important attributes of higher quality base oils include additive solubility, toxicity and biodegradability, soot dispersancy capability – an increasing issue with spark-ignited direct-injection engines; and purity.

And tougher engine oil requirements are not just a North American, European and Japanese phenomenon, said McMillan. More restrictive requirements are being enacted worldwide, requiring better lubricants and better base oils.

Jim Linden, who is responsible for specifications for GMs automatic and manual transmission fluids, axle lubes, greases and other lubricants, described the impact of upgrades in those fluids.

GM wants fill-for-life for all applications, said Linden, who is based in Warren, Mich. In the future at least, 150,000 miles will be considered life for transmissions in severe service.

In April 2005, GM introduced its trademarked Dexron-VI automatic transmission fluid, a significant upgrade over the previous spec, Dexron-III. The new fluid was required by the reduced sump volumes, higher fluid turnover rates and increased energy densities with the companys new transmissions, Linden said. The new transmissions also have less airflow, and thus less cooling capacity, and more aggressive electronically controlled converter clutch usage. New six-speed transmission designs demanded a new fluid, which also had to be back-serviceable.

With premium ATFs, said Linden, base oil quality is vital to fluid performance. Fords Mercon-V calls for Group II-plus; DaimlerChryslers Mopar ATF+4 calls for Group II-plus or III; and Dexron-VI generally needs Group III quality.

The Dexron-VI ATF specification does not specify a base oil quality level, Linden noted. However, the viscosity and oxidation requirements make it difficult to meet the spec without using at least a Group III or Group II-III combination.

Turning to axle lubricants, Linden said, At GM and in the industry there is a trend toward lower viscosity grades. Fuel economy improvements are the driver.We see an imporvement of 0.6 percent in fuel economy with such [fuel efficient] axle lubes, and we believe an additional improvement of similar magnitude is possible with additional axle lubricant optimization,Linden told Lube Report.

High viscosity index base oils allow good low-temperature performance without sacrificing high-temperature durability, Linden continued. We have seen temperature reduction through base oil selection. And fill-for-life will be available for all rear-wheel-drive vehicles with high quality gear lubes.

Base oils need to be part of the engine oil equation, Linden said in summary, and improved base oils are necessary for extended drain intervals. Lube requirements outside North America, Europe and Japan are likely to increase rapidly over the next decade, with vehicle technology improving. Fuel economy and emissions regulations will demand better lubes, and base oil technology needs to improve to meet increased vehicle technology demands.

Finally, Linden concluded, high quality base oils will be necessary to meet current ATF and axle lubricant requirements.