Things are moving fast in the motor oil business. There have been more changes in basic oil types in the last 10 years than in the previous three decades, and still another is due out soon. Called CI-4, the new oil will be the fourth since 1990, and still another is due less than four years from now.

The new oils are the result of ever-tightening limits on diesel exhaust emissions, which have required fundamental redesigning of engines that put new stresses on oil. The current diesel motor oil, called CH-4, has been in use less than four years, and its replacement is almost upon us. CI-4 (formerly called Proposed Category 9) will be needed for the next style of light-, medium- and heavy-duty diesels due out between October and January 2004. Federal rules require these engines to produce about 50 per cent less nitrous oxide, or NOx, than current diesels.

The new, cleaner diesels will be more complex and expensive. Builders aren’t saying how much more they’ll cost, but it’s likely to be US$2,500 or more, each. This, along with unproven performance and durability, is causing some fleets to plan to avoid them. Some fleets may buy early to get pre-October diesels, or not at all, choosing instead to keep what they now have and perhaps buy some of the many used trucks on the market.

Most diesels will cut NOx with “cooled exhaust gas recirculation (EGR).” The ’99 and later engines, for which CH-4 was developed, cut NOx mainly through retarded timing.

NOx can be cut further by reducing combustion temperatures, and engine builders have decided that cooled EGR is the most effective way. Small amounts of exhaust gas will be piped to the chambers to displace oxygen; less oxygen means cooler combustion. Before going to the cylinders, some of the exhaust gas’s heat will be absorbed by the engine’s coolant. Thus the term, cooled EGR.

Some engine makers are trying to put a happy face on the situation, noting that the new diesels will be more responsive for drivers and deliver fuel economy as good as now. But they’d rather do without it, because it’s complex and costly.

You will see diesels with cooled EGR by later this year, and by early 2004 most truck diesels will have it in one form or another. One exception is Caterpillar, whose ACERT (advanced combustion emission-reduction technology) will employ faster electronics, better combustion efficiencies, and a catalytic converter on the exhaust.

Diesels with cooled EGR will run hotter and produce more soot than today’s models. They’ll also produce more acids that can attack internal parts. CI-4 motor oils due out this summer will be formulated to take the greater loads and protect both new and existing diesels, say petroleum engineers. Most producers have to reformulate their oils to meet CI-4 requirements; the exception is Chevron, which says its Delo 400 reformulation in 1998 also meets the 2002 standard.

More heat, soot and acid will be formed during combustion in most of the new diesels, say oil producers. Heat seems the biggest threat because it breaks down oil. Heat from exhaust gas will be transferred to engine coolant, and when coolant gets hotter, oil gets hotter.

Oil oxidizes as it gets hotter. The oxidation rate doubles with each 10C (18F) rise in temperature. Oil thickens as it oxidizes, and it does not thin out again as it’s pumped and sheared – the cutting action oil faces as it moves through gears and tight passages in the system.

Engine oil will probably have to run at up to 260 degrees Fahrenheit in the sump, compared to 220 degrees as is now typical, the oil producers say. Additional antioxidants in some oils will compensate for the higher temps.

Soot levels in crankcase oil will rise to as much as 10 per cent by volume, vs. 1.5 to five per cent now and one to 1.5 per cent in pre-’98 diesels, say experts. Oil analysis now recommends an oil change when soot reaches three per cent, so more dispersants will keep soot in suspension so it doesn’t “clump.”

Higher soot levels threaten long oil change intervals preferred by some fleet managers. However, the additional dispersants should allow drain intervals to at least stay as they now are and in some cases extend them farther. If you are among the many operators who change oil more often than required (which really isn’t necessary), you should be more than safe. The best way to know, of course, is through regular oil analysis. As you might suspect, not every diesel will produce more soot. Test diesels run by ExxonMobil, as well as the type of tests that two manufacturers have chosen to qualify oils for their engines, indicate to some engineers that Cummins engines will make more soot, Macks might make more and Detroits may make less. Cats won’t use EGR, so should not have a soot problem. It’s too soon to know about other light- and medium-duty diesels which, by in large, won’t face EGR until 2004.

Exhaust gasses from the EGR system will carry sulfur and nitrogen into the cylinders, forming sulfuric and nitric acid – both nasty, corrosive compounds. The acids will move past the rings into the crankcase. Acids attack any metals they touch, so they have to be neutralized through increased alkaline reserves in the new oils, experts say.

Sulfuric acid will remain a problem as long as relatively high-sulfur fuel is out there. Most of today’s fuel can have as much as 500 parts per million of sulfur. In summer of 2006, the Environmental Protection Agency, which also sets federal exhaust emissions limits, will require fuel sulfur to be cut to 15 ppm. This should reduce the acid problem.

Ability to neutralize acid is among the things indicated by any oil’s Total Base Number. TBN also describes detergents and other additives, as well as the oil’s stamina as it works to combat contaminants. TBN as a whole is a bigger issue with CI-4 than the individual problem of soot, some engineers think.

Will CI-4 be okay for all engines, including now-current models?

Yes.

Like previous oil types, most CI-4 formulations will be “backwards compatible,” but read the label closely to be sure.

An industry committee led by Jim McGheean, ChevronTexaco’s manager of engine oil technology, has finalized specifications for CI-4. Products that meet the specs already available, and others certainly by early this summer. This will allow oil marketers to produce and certify their new oils by the time the engines go into production in October ’02.

CI-4 will appear in the familiar API “donut” label that’s stamped on oil containers. Makers of premium oils always note that the category describes minimum specifications, and lesser oils that qualify for it may not have all the properties that a user wants. Premium oils go beyond the minimums, so consider the entire product.

Synthetic lubricants will also meet the new category’s requirements. As now, the major benefits of “synlube” is in reduced friction, which will allow easier cold-temperature starts and possibly better fuel economy. Synlubes also stand up better to extended oil drain intervals, for those who want them.

There have been major changes in motor oil for gasoline engines, as well, sources say. A new category, SL, replaced SJ oil last July. SL oil is more robust so it can run longer between drains; has lower friction to improve fuel economy; and is less volatile for lower consumption, which protects exhaust catalysts from damaging oil smoke.

The “S” in gasoline-engine motor oils means service, as in servicing the engine by adding oil, vs. factory fills, for which each manufacturer has its own specs. (Some think S means spark, which of course is how gasoline is ignited.)

By the way, category names are established by the American Petroleum Institute. In the API naming scheme, the second letter progresses up the alphabet with each new category, so “I” logically follows “H” (as in the cur
rent CH-4 designation).

You may know that the “C” in the category name means commercial (some say it means compression, as in the diesel’s compression ignition). The “4” means four-cycle, the type of diesel this oil is designed for.

CG-4, the ’94 diesel engine oil, replaced CF-4 just as CE replace CD. Note that it took 28 years to move from CD to CE, but oils went to CF-4, CG-4 and CH-4 in only eight years, and four years later we’ll have CJ.