TORONTO, Ont. – Oil probably deserves its nickname of black gold. After all, truck engines would meet a quick end without this great defender of metal.

But engines designed to meet ever-tightening emission standards are pushing the limits of chemistry.

The current generation of oils was rushed to market in 2002 to handle the higher soot loads that accompanied a U.S. Environmental Protection Agency crackdown on NOx levels in exhaust.

“And that whole process was crammed,” says Castrol spokesman Jim Burke, suggesting API CI-4 formulas were initially planned for 2003.

At the time of the early release, the technology needed to meet 2004 emission limits was still a mystery.

Now that 2004 engines are here, a whole new series of challenges have emerged in the oil pan.

Consider Exhaust Gas Recirculation (EGR) designs, which cool exhaust gases to 250 F from as high as 1,200 F before injecting them back into cylinders.

An unwelcome byproduct of the process comes in the form of acid, created by combining the resulting condensation with the sulfur found in diesel.

And acid can cause corrosion in the crankcase and on bearing surfaces.

The science behind the solution seems as simple as popping Rolaids.

High acid levels need to be neutralized, and in an EGR engine, the relief comes in the form of higher ash levels in the oil.

But not everybody uses EGR. Caterpillar, which tackles NOx with such things as valve timing in its Advanced Combustion Emission Reduction Technology (ACERT), sees the higher ash levels as a source of deposits on piston rings.

The maker of yellow-coloured powerplants now demands a maximum level of sulfated ash through a standard known as ECF-1; other manufacturers including Cummins call for a minimum level with a test known as Cummins CES 20078.

Oil chemists, for their part, are left with a narrow target.

Another unwelcome byproduct of EGR comes in the form of additional soot – and a soot-loaded lubricant won’t flow very well, leading to damage from contaminants and metal-to-metal contact.

Granted, engine manufacturers were prepared for higher soot loads as early as 2002, and many responded by requiring more oil changes.

And Mack increased the size of its sumps to ensure a larger supply of oil that could handle a larger load of contaminants.

But it seems that not all soot is created equal.

“The type of soot in the EGR systems is a different quality,” says Clinton Smith, a technical advisor with Imperial Oil, referring to problems first found in Mack’s vocational engines, leading to the EO-N Premium Plus ’03 guideline. Chemists are still baffled about the exact difference, but the new soot seems to trap more of the dispersants designed to keep it suspended in the oil, says Gary Parsons of Chevron Texaco Global Lubricants. (There need to be enough dispersants to maintain the oil’s viscosity.)

“It acts like sandpaper,” adds Petro-Canada category manager Jim Abrams, referring to the impact on components.

To compound matters, yet another problem is created with the higher heats associated with EGR, says Alex Bolkhovsky of ExxonMobil.

Oil oxidation (the rate at which it breaks down) doubles with every 18 F increase in temperatures, he says.

And most EGR engine designs have crossed the threshold.

All of these problems are solved with a fresh supply of oil, but those looking to save money by extending the time between oil changes haven’t exactly welcomed shorter drain intervals.

And the only way to find the outer limits of a drain interval is to keep a watchful eye on contaminants.

“You can get test results for $12 to $15 or as high as $40, depending on what you’re trying to measure,” says Abrams, referring to oil analysis programs.

But any analysis requires a sample to be pulled and sent to a lab, while results have to be interpreted once they arrive.

“That all takes time and effort,” says Shell Canada product manager Steve Miller.

And that has to be balanced against the cost of additional oil changes and the income lost when a truck is in the service bay.

A new generation of oils known as API PC9.5 is expected to be introduced this fall, to meet the needs associated with 2004 truck engines.

But the biggest challenge is yet to come.

While the U.S. Environmental Protection Agency has been focusing on NOx, a new set of standards coming in 2007 will also call for a 90 per cent cut in particulate matter – the cancer-causing particles that have been the focus of regulators in Europe.

Particulate traps are expected to handle the newest contaminant, but that creates another problem for engines from companies such as Cummins and International that will continue to use EGR.

The same ash used to control acid in an EGR engine will destroy a particulate filter. Such damage could cost more than $8,000 to repair, Smith says. And if you put a low-ash oil into an EGR engine with high acid levels, “you’ll probably wear the damn thing out.”

Some help will come in 2006 with the introduction of Ultra Low Sulfur Diesel, which will limit sulfur levels to 15 parts per million, compared to existing levels between 350 and 500 ppm.

That will reduce acid levels somewhat, but the critical ingredient of sulfur still exists in some of the oils themselves.

The new standards suggest the need for a radically different oil. But new chemistry comes at a cost.

The only question is whether that will come in the form of a higher price, or a lubricant that can only be used in engines built after 2007. Smith suggests the trucking industry will balk at the idea of two different oils.

“Drivers have little interest in which oil goes in which engine,” he says. “All they want to do is clock miles.”

Parsons counters that fleets might be willing to stock different formulas if the alternative is a 50 per cent increase in the price. “Then maybe backward compatibility isn’t an issue.”