The latest lubricants for diesel engines are designed to handle everything better than their predecessors-soot, heat, acids, oxidation, the works. That’s important: the engines designed to meet the U.S. Environmental Protection Agency’s latest emission standard are demanding. They run hotter, and count on the oil to help disperse that heat. Their retarded fuel injection timing loads more soot into the oil, and the exhaust-gas recirculation technology most use introduces sulfuric acids into the cylinder.

It’s enough to give you a crankcase full of jitters. Too much soot can lead to valve bridge and overhead system wear, plugged filters, bearing failure, sludge, and lost fuel economy. Sulfuric acids can corrode cylinder liners, rings, and bearings.
In fact, two years ago, there were concerns that EGR-equipped diesels would require oil so radically different that it wouldn’t work with older engines. There were also predictions that the price of these lubes, designated CI-4 oils by the American Petroleum Institute, would be astronomical.

Fortunately, nine months after the EPA’s October 2002 deadline, neither concern seems to have materialized. Most of the major lube suppliers reformulated or introduced motor oils meeting API CI-4 well in advance of the EPA deadline. And they’re not only backward compatible with your older diesels, they seem to be better for them.
Dan Arcy, product manager for heavy-duty lubricants at Shell, offers an example: The CI-4 test for volatility-basically the amount of oil burned off at high temperature, he says-allows no more than 15 per cent. For the previous standard, CH-4, the benchmark was 18 per cent. That means your oil consumption rate, and more importantly, the potential for deposit formulation, is less than what it used to be. The only cautionary note we heard from the oil makers was from Castrol, which says some CI-4 oils use a relatively high sulfated ash content, which has been shown to generate piston deposits.

As for any cost increase with CI-4 oils, it’s hard to tell what’s directly attributable to R&D that went into new formulations. “There was a lot of money put into developing these oils,” says Arcy, “but the market drives the price. When it comes down to it, the difference in the cost of CI-4 versus CH-4 is minimal.”

That’s the good news. The bad news is, even with these better oils, EGR engines may put a crimp in extended oil drain programs. Extended drains are one of the most common ways to save money on oil changes.

At this date, the jury is still out on how long you’ll be able to extend oil drains with EGR engines. Engine and oil manufacturers alike are generally cautious about potential damage from the additional acids. Others are optimistic, saying you may still be able to safely extend drains by carefully monitoring the oil.

One thing everyone agrees on is that because there is limited fleet experience with EGR engines, used-oil analysis is vital to find the right drain intervals. Gary Parsons, global consumer and transport segment director at ChevronTexaco, recommends that wear metals, viscosity, TBN, and soot levels be used as indicators of when the oil has served its useful life.

Check with your engine manufacturer about recommended drain intervals and how exceeding them might affect your warranty. High-quality full-flow/bypass engine oil filters may help remove impurities and compromise extended drains. Whatever you choose, Parsons says, look at the total cost of ownership for the oil. Products that seem more expensive may actually reduce costs overall if you can extend service intervals, improve fuel economy, and reduce downtime.

Jim Abram, manager of heavy-duty oils and commercial products for Petro-Canada, explains it this way: “People think of oils as commodities. But all engine oils are not the same. You can’t choose an oil on price alone. You have to look at its performance characteristics.”

Most premium oils not only meet the CI-4 requirements, they exceed them. They also meet or exceed requirements of various engine makers, such as the Mack EO-N PremiumPlus, Cummins CES 20078, and Volvo VDS-3 tests. That means better corrosion protection, better soot dispersancy, and better oil consumption control, which lead to better performance and engine protection.

Synthetics remain an option if you want to extend oil drain intervals. They also offer faster, safer starts in freezing weather and handle hot weather better. But they cost more than mineral-based oils.
Extended drains can offset the cost. Petro-Canada has experience with extended drains as much as four times longer than conventional oils when using synthetics. Better cold-weather starting can extend the life of your engine, battery, and starter. Drivers will lay off the ether. Synthetic blends like Petro-Canada’s Duron and Chevron Delo 400 Multigrade provide many of the benefits of a pure synthetic at a lower cost. Some premium oils use highly refined Group 2 base stocks, resulting in performance their manufacturers say rivals synthetics.

“Synthetics cost more and don’t provide extended drain or fuel economy benefits when compared to performance products formulated in Group 2 base stocks,” says ChevronTexaco’s Parsons.
In extreme low temperature conditions, however, full synthetics do offer an advantage over mineral oil products. “If someone comes in and says they can save you money by going to synthetics, you should do engine oil analysis and see if the oil stands up to the claims being made,” says Petro-Canada’s Abram. Good advice for other premium oils, as well, not just synthetics.

With CI-4 oils on the market, the work is hardly over for lube suppliers.
A committee at the API is already considering Proposed Category 10, or PC-10. Due in 2006, this will set standards for oil used in 2007-model diesel engines, which will need to burn ultra-low-sulfur fuel and use exhaust aftertreatments to meet emission targets.

Engineers say the challenges to reach the next level of oil performance are daunting and could require a whole new batch of additive chemistry, which might not be compatible with engines other than the ones they are specifically designed to lubricate. Such a scenario would add confusion and cost for fleet owners, because they’d have to stock two types of oil and make sure the guys in the maintenance bay are dispensing the right stuff. But then, that’s what they said a few years ago about CI-4. A lot can change in three years.