Tribologists are very important folks these days. No, they’re not social historians studying the Bushmen of the Kalahari Desert. They’re the technical wizards who work so hard to create the oil your engine needs to live longer than a mile or two.

And they’ve never been busier.

Thanks to increasingly stringent emissions regulations, which are going to get tougher still, engine makers have had to make huge changes to the way
combustion occurs and especially to the way its byproducts are dealt with. It’s astonishing that, over the past couple of decades, heavy-duty diesel engines have gotten better in just about every way, not just in terms of pollution. They’re making more useable power than ever, they’re easier to drive, and they’re almost infinitely programmable. If you want a flat torque curve from 1100 all the way to 1700 rpm, no problem. They also last an awful lot longer.

On the emissions front, modern diesels produce a third less carbon dioxide than gasoline engines. Today, NOx emissions have been reduced by 70%.

Particulates have been reduced by 90% during the last 10 years. And, better yet, diesel emissions will be reduced by an additional 50% over the next decade.

“Compared to alternate power sources, the environmental impact of diesel already is minimal, and it’s only going to get better,” says John Campbell, performance engine products manager at Caterpillar.

And, of course,diesels are more efficient than ever. Your trucks can still get 4.0
miles per gallon if you allow them to be driven that way, but it’s no great challenge
to cut that consumption in half. Or better.

All that progress is pretty obvious. But every major change in emissions regs, with its attendant change in combustion engineering, also brings the need for a new
engine lubricant. That’s a much more subtle matter, but it’s no less remarkable.

“The whole lubricants industry is being driven more and more towards higher
standards, where yesterday’s premium-grade capabilities become today’s minimum standards,” says Peter Mack, manager of automotive products marketing at Petro-Canada Lubricants.

Lube refiners have their work cut out for them now, with the work that 2002
emissions regs have forced on them.

“Our industry has seen more successive emission regulations in the past 10 years than we saw in the prior 40 years,” says Don Carver, legendary oil expert and program co-ordinator for ExxonMobil’s ‘Smartlube’ program. “And we’ll see many
more changes again in the next six to 10 years.”

For 1999, engine makers could only meet lower nitrous-oxide (NOx) demands by retarding injection timing, but that meant reduced combustion temperature and hence substantially higher levels of soot added to the crankcase oil. It’s not hard to fathom why. Retarding the injection allows the piston to advance down the cylinder
a little before combustion is complete. The actual amount is only around 30
thousandths of an inch, but the out-of-the-combustion-bowl process means trouble
by way of soot. It’s basically unburned fuel, and it’s nasty.

Soot levels increased by 100% or so in those retarded engines, — going up to a
whopping 600% in some cases — which demanded a new oil classification even
beyond the American Petroleum Institute (API) CH-4 standard introduced in late 1998. The key challenge: keeping that soot in suspension.

Two engine makers had already developed their own more stringent oil specs by
then. The Mack EO-M and Cummins CES 20071 tests improved oil’s ability to
keep soot in suspension. Then they went one better to create the EO-M Plus and
CES 20076 tests, aiming to further ensure long-term engine durability. They’re
tough enough that the oil industry itself has gone on to worry about the effects of
the 2002 regulations (see below).

The rigorous Cummins M11 high-soot test, for example, measures the wear on the valve bridge where the rocker bears. As the rocker presses down on the bridge it slides across the surface, and a lube oil heavily laden with soot will act as an abrasive on engine surfaces unless the soot is well dispersed. Similarly, soot contamination will clog filters and leave sludge deposits on the rocker cover.

These are elements of the Cummins M11 test and they quickly reveal shortcomings in an oil’s additive package.Oils meeting these new Mack and Cummins standards have become known as CH-4+. Compared to earlier CG-4 oils, they offer better control of soot-induced wear, improved filter performance,
better viscosity control, and easier low-temperature pumping, among other gains.

Straight CH-4 oil can manage a maximum soot content of 5%, Don Carver notes, and the newest CH-4+ oils go to 7.5%. Previous API classifications handle progressively less – 1994’s CG-4 can manage 3% and CF-4, from 1991, just 1.5%. Earlier oils were CE and CD, from 1988 and 1970 respectively. Note that
we’ve seen four API classifications in the 1990s.

New Categories
The American Petroleum Institute is the agency that decides when a new lube-oil
category is required. The process starts with a request from engine manufacturers; extends through a review that determines whether circumstances have changed to such an extent that the category is really essential; and leads to a task force design of the testing and performance requirements that oils complying with the category must meet.

John Holuk, technical advisor/lubricants, at Shell Canada, explains the process of determining the specifics of a proposed new standard. First off, lube refiners
learned long ago that they couldn’t go their own way.

“It probably costs an oil company between $250,000 and $500,000 to run the tests that get a heavy-duty engine oil approved if there’s been any significant change to the standard,” he explains. “So it certainly made sense to develop a set procedure to handle the evolution of standards.”Each engine manufacturer, as their models change, will become aware of the various ‘nuances’ in how those power plants operate — their strengths and
weaknesses, if you will — and they’ll release a set of performance criteria that they feel the lubricant industry must meet in order to adequately address the needs of that engine.

“And each engine maker will propose certain engines to use as test beds. These
engines nowadays usually are found at certain commercial test facilities around
the United States, rather than in-house at each oil company. It’s more
cost-efficient to contract with these test centres: you send them a quantity of your
lubricant; they’ll run the desired tests to a very structured protocol that they use for every client; and then they’ll send you the results.

“The consensus of performance criteria that becomes a standard like CH-4 will
last perhaps three or four years, but even that’s not the end of it,” Holuk notes.

“The various engine manufacturers typically also establish their own standards, much of which will be incorporated into something like CH-4, but they’re not necessarily identical. If an engine maker feels that they need to have something out on the street to protect a given engine they’re producing, and the current API-sanctioned standard has some gaps in it – or the latest version isn’t ready yet – then they’ll issue their own standard.”

Once the criteria are published, API allows a year for all lubricant suppliers to complete testing and certification before it licenses the supplier to use the API ‘donut’ on its labels, with the category number inside the ring to show that lube oils meet the new category definition.

It’s the American Society for Testing and Materials (ASTM) that actually develops the testing and performance criteria for heavy-duty oil classifications. It includes
oil, additive and engine manufacturers.

To qualify for any category, oil is run in certain kinds of engines under exacting
test conditions. Oils failing to meet performance levels can be denied certification
or, somewhere along the line, stripped of certification if makers don’t make
corrections. Each refiner formulates its oil to meet a classification’s minimum
performance requirements, so two oils that have earned the CH-4 or any other label may not be equal in performance. Formulations — and performance — will differ among refiners.

To put all this in a practical context, the Cummins recommendations for 1999 N14 Plus engines in normal duty (5.5 to 6.5 mpg and under 80,000 pounds gvw) allow 20,000 miles between oil changes with CG-4 lube, 30,000 with CH-4/CES 20071,
and 35,000 with CH-4+/CES 20076. A 1999 Signature engine can go out to
40,000 miles with CES 20076 oil.

Incidentally, the ‘C’ in CH-4 means compression ignition, as in diesel, and the ‘4’
refers to four-cycle, the type of diesel this oil is designed for. The ‘H’ denotes
progression from one standard to the next.

New Hurdle
The next oil type, tentatively called PC-9 (PC stands for Proposed Category) and likely to get the CJ-4 name formally, will be needed for the heavy-duty diesels due out in October 2002. By U.S. decree, they’ll produce about 50% less NOx than
current engines. All of them will need cooled exhaust-gas recirculation (EGR) to
do it, and that means the oil refiners are mighty busy.

Some engine makers feared that they couldn’t pull this off, and it’s not a done deal
yet, but the lube test requirements have been established and all ASTM labs now have test engines. Formal testing will start this month and end some time in early
2001, with the CJ-4 standard likely ready for market in early 2002. It looks like
there will be three separate engine tests – the Mack T10, Cummins M11 with EGR, and the Caterpillar 1Q by name.

Details are understandably scarce, but it seems that a typical 2002 EGR system
will siphon a small amount of exhaust gas from the turbo, run the gas through a
special water-to-gas heat exchanger, and then mix it with clean inlet air in the
charge-air cooler. From there the cooled air-gas mixture will go to the engine’s
combustion chambers where it will help cool the combustion flame, by excluding a
portion of the oxygen, to reduce NOx.

How much exhaust gas will be recirculated? It’s not known, but some industry experts are suggesting 12% to 15%. It is known that injection pressures will be higher still, and they’ve been rising steadily since the emissions challenge first
began as engineers strive for ever more efficient combustion.

For heavy-duty diesels, there are some major problems getting cold EGR to work.

For one, there’s the problem of getting the gas to go into the turbocharged inlet
stream — a bit like getting balls to roll uphill. For another, there’s the need to cool the gas from its 1000° or so temperature down to around 200°. Neither of these
problems exist with current EGR applications in gasoline engines, so there’s little
technology to draw from there, either in designing the engines or the lubes that will allow them to live at the same durability levels as today’s diesels.

ExxonMobil’s Don Carver is pessimistic about all this. “Cold EGR maintains fuel economy, but you have to be careful not to cool too far and get condensed
sulphuric acid,” he says. “So it’s more complicated than previous changes.

“EGR brings top ring and liner wear, resulting in a dramatic decrease in engine
durability. Also, high EGR means rapid Total Base Number degradation and a
four-times soot increase. That results in oil thickening.”

Today there are EGR engines running, and even though none are in their final form, it’s pretty evident that Carver’s prediction will be borne out. There will be increased corrosive acids in the oil, a marked increase in soot, and increased injector slider wear.

Also, since the engines will have to cool the exhaust gas, with predictions of
anything up to an additional 40% increase in heat rejection, engines and engine
compartments are expected to run hotter. That will lead to increased oxidation in
the oil.

To handle all the anticipated changes and to gain a measure of comfort against the EGR demands, additional testing is included in PC-9, bringing the total to 13 to satisfy the needs for oil certification.

Dan Arcy, Pennzoil’s product manager for heavy-duty engine oils, points out the limit for the maximum soot in diesel lube was pegged at just 1.5% in 1993 when
CF-4 came in. The 2002 standard has a requirement to carry up to 10% soot.

“Oil is going to have to protect even more. Imagine, if you have a crankcase with
11 gallons of oil, at 10% soot, one gallon of crankcase capacity is soot,” he says.

“This would be a worst-case scenario — stop-and-go city traffic — but it shows the
great improvements in oil over just the last few years.”

Arcy notes that CJ-4 oil it will be backward-compatible, meaning the new oils will
be useable in pre-2002 engines.

Perhaps surprisingly, it also seems that there will be no degradation in
drain-interval capability with CJ-4 oils.

Work is already underway on the next emissions hurdle, set for 2007. This one is
so challenging that some industry engineers have referred to it as a new
paradigm. The proposed emissions levels, published in April, will likely require a continuation of EGR with additional particulate trap and NOx catalyst
technologies.

To have lubes ready for 2007, ASTM is already working on PC-10. The demands of those technologies may well mean the end of backwards compatibility for new
premium oils, says Arcy.

Oil as Component
Lube oils are obviously an increasingly important part of the total emissions
strategy. More and more, they’re a key engine component, fundamental to the
durability of an engine’s pistons, rings and bearings. To meet the emission
standards of today, tomorrow and the future, lubes have to have the very best
soot-handling and anti-corrosive properties the lubricant industry can muster.

At the same time, however, truck users have been looking for performance gains as well, especially in longer drain intervals. The fact that oils have managed to
allow stretched intervals, while meeting all those other challenges, is really quite
remarkable. But it does mean that this is no time to try to save a buck on cheap
oil.

It used to be you could get by with a lesser-quality lube. No more. Its job has
become too important, with less margin of error. A lube oil’s additive package,
most notably the detergents and dispersants that keep soot from building up on
engine surfaces, has to be awfully good.

The demands of engines today also dictate that the category of oil you use has to be matched precisely to the level of your engine’s technology. Engines from 1998
need CH-4 oils, and 1999 models need CH-4+ oils. By 2002 you’ll have to be
using PC-9/CJ-4 if you want the same level of engine reliability and durability
you’ve enjoyed over the last decade.

You may be concerned about the rising cost of engine lubes, but you’ll appreciate
that the rocketing price of crude oil has had an affect on both oil base stock prices
– they’ve doubled – and on oil-derived additives used in blending top-quality lubes. Other non-crude-based chemicals have been affected by tightening supply,
which drives up their price.

Premium oil marketers have also raised prices to help pay rising research costs
for next-generation lubes. For instance, a normal Cummins M11 test that ran 200
hours now requires 300. The cost of meeting Mack and Cummins specs has
increased as much as US$60,000 to $80,000 per test. Some of the upcoming
tests may require 500 engine hours or more, we’re told.

But more than ever, when you choose an engine oil, you’re going to get what you pay for.