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If youve been around as long as I have, you may remember a time when dedicated oils were always needed for specific engine types; diesel engines differed enough from gasoline engines that each required its own oil. Problem was, if your fleet had a mix of both gasoline and diesel engines, you had to inventory twice as many engine oils.

According to sources, in the late 70s Chevron Oronite developed the first so-called universal oil, which met both American Petroleum Institute SE (gasoline) and CD (diesel) categories. Labeled as API SE/CD, these oils were able to successfully protect engines regardless of the fuel used. They even could lubricate the old two-cycle Detroit Diesel engines which required oils with sulfated ash content of less than 1 percent. They also met some transmission oil standards.

Soon, all the additive suppliers and oil marketers got on board and the universal oil juggernaut was launched.

Now, over 30 years later these venerable oils are on the edge of extinction. What are the evolutionary forces pushing them to the edge? Is there hope for them or will they go the way of the dinosaur (and are they already dinosaurs)?

Engine manufacturers have brought up the issue of universal oils before, and have voiced concerns repeatedly about what they consider to be formulary compromises that are made to address all engine builder requirements.

On the heavy-duty side, look again at sulfated ash: While Detroit Diesel wanted restrictions on ash content due to port-plugging concerns, Caterpillar wanted higher ash content oils to protect against piston deposits and to neutralize the acidic components in exhaust gas blowby.

As for the light-duty passenger car folks, universal oils phosphorus and ash content have been thorns in their side for a number of years. This is primarily due to the impact these chemistries have on exhaust catalyst systems.

Of course a secondary reason light-duty OEMs frown on universal oils is the viscosity grade. The preferred viscosity for heavy-duty oils (and the one most universal oils meet) is SAE 15W-40. OEMs want light-duty engines to use SAE 5W-30 or lighter.

From the lubricant marketer and customers view, universal oil has great benefits. The fact that a single oil can lubricate all types of engines means fewer products to buy, no mixups in oil application, larger quantity purchases, fewer SKUs to maintain, and less product storage requirements. Any time consolidation of products is in favor, nothing could be better.

However, over the last 30-plus years marketing strategies have changed. There is now a trend to specialized branding for various applications. Just go to your local big box store and look at the motor oil shelves. In addition to the standard brand/viscosity mix, youll see 4X4 oil, synthetic and synthetic blend, high-mileage and high-endurance oils, to name just a few. When the next light-duty upgrade, ILSAC GF-6, hits the shelves there also will be a new vis grade: SAE 16, offered either as SAE 0W-16 or perhaps 5W-16.

The heavy-duty products on those shelves may be conventional SAE 15W-40 or a synthetic 5W-40. With PC-11, the next upgrade for diesel engine oils, youll see more 10W-30. And while the store shelf is not a trucking fleets lubricants storage area, it does reflect the kind of diverse thinking that will be going on.

Additive suppliers get a lot of credit for the continued availability of universal oils. They have been able to successfully include both S and C category performance in keeping with API guidelines. In fact, heavy-duty oils up through todays API CJ-4 category almost automatically are API SL, SM or SN as well. It so easy that even OEMs – such as Caterpillar, Chrysler, General Motors and Ford – carry an API-licensed universal oil in their branded lineup.

Universal oils have lived on in every previous category upgrade, a testimony to their survival skills. They have done it by adapting to meet the latest requirements of both diesel and gasoline oil categories; but it gets tougher each time. In fact, the combination of PC-11 and GF-6 may well be the asteroid impact that seals their fate.

What could be so drastic that it would not allow both categories to be covered by a single oil? Well, I already mentioned two reasons: viscosity and phosphorus.

PC-11 is calling for two distinct products. One will be a traditional SAE 15W-40 that is fully backwards compatible with earlier categories; the other wont. Remember that one of the guiding principles of API 1509, the Engine Oil

Licensing and Certification System, is that any new category must be acceptable for use in earlier engines. This is to prevent any systemic lubrication problems developing in older vehicles. One of the backwards compatible requirements is that the high temperature, high shear (HTHS) viscosity not drop below 3.5 mPa-s.

However PC-11s second proposed product has lower HTHS viscosity, likely to be somewhere between 3.0 and 3.5 mPa-s, as a way to improve fuel economy.

Bottom line, the fuel-saving version of PC-11 wont meet the HTHS viscosity requirement for backwards compatibility. It may not be viscous enough under the operating conditions of older vehicles.

The same viscosity issues confront the GF-6 gasoline engine oil upgrade. Here too, there will be two new oils, one which meets the backwards compatibility criteria and another which will be lower in viscosity than the minimum for earlier categories.

The new oils also are diverging on phosphorus. Like earlier API commercial categories, PC-11 has a proposed phosphorus limit of 0.12 percent maximum. This provides the wear protection needed in diesel engines and is the preferred phosphorus level of heavy-duty engine manu-facturers. However, GF-6 oils will limit phosphorus to between 0.06 and 0.08 percent maximum.

So we have this rather complex mix of problems. On the one hand, PC-11 needs to add a fuel econo-my (lower-viscosity) grade which most people believe will probably be satisfacto-ry on an engine perfor-mance basis but below the HTHS viscosity associated with the traditional prod-uct, and therefore not backwards compatible.

Meanwhile, GF-6 has much lower HTHS viscosity requirements and less phosphorus than PC-11. It will be almost impossible for GF-6 oils to also meet PC-11. What to do?

In Appendix G of API Document 1509, footnotes specify that engine oils which meet API SL, SM and SN can waive the phosphorus limits as well as the Sequence VG, Gellation Index and Ball Rust tests – if the category is preceded in the API donut by API Category CI-4 or CJ-4, as shown at left. There is a caveat, API reminds us: C category oils have been formulated primarily for diesel engines and may not provide all of the performance requirements consistent with vehicle manufacturers recommendations for gasoline-fueled engines.

The OEMs see this as a tacit admission that universal oils might not be the best thing for the marketplace. They want to see these waivers eliminated, so that a product that meets C categories also should meet all the requirements of S categories in order to be accepted as a universal oil.

From a formulators standpoint, that will be a tall order since heavy-duty engine oils need the current 0.12 percent phospho-rus levels to protect against wear in heavily loaded areas of the engine. Thats not to say it cant be done, but at what cost? A PC-11 SAE 10W-30 engine oil with a maximum of 0.08 percent phosphorus will be a challenge to even the most creative and proficient additive supplier.

One solution proposed by oil marketers is a continuation of current practice. Namely, that only viscosity grades not specifically noted in ILSAC GF-6 or earlier categories (SAE 0W-XX, 5W-XX and 10W-30) would continue to be acceptable as universal oils, with the waivers noted. As with current API 1509 guidelines, the API C category would come first in the donut, fol-lowed by the S category. Notably, GF-series oils are not involved except for the SAE 10W-30 grade, which would overlap and actually might be the most difficult issue to resolve.

So here is another confusion point. The GF series of engine oil specifications dictate all the engine test performance criteria for the corresponding API S category – all, that is, except for fuel economy limits, which GF oils mandate but API S categories dont. Universal oils, identified in the donut as satisfying both C and S, do not make it explicit to consumers that they could forgo the fuel-economy gains of GF-series oils.

The OEMs are concerned that S category oils will find their way into light-duty gasoline engines because, among other things, there is no readily visible means of identification. If that happens, the potential result would be catalyst contamination from phosphorus and a loss of fuel economy.

Today, many states run emissions checks on in-service vehicles in order to renew their registration. A failure on emissions means costly repairs for owners and lots of pressure on the OEMs. They much prefer, and rightly so, that the proper oil be used in the engine; one which will minimize any concerns.

So, the OEMs would prefer that the whole universal oil concept go away. If there are no universal oils, then there is no problem. They would also like to see API discontinue licensing older but still-active S categories like SJ, SL and SM. That would eliminate older universal oil types, too.

The oil marketers dis-agree since they see a continuing need for these oils in domestic and overseas markets. The older oils are fully licensed and have demonstrated performance. They are also required by some OEMs, and even if the category is discontinued the oils will still be around.

For my part, I really wonder what percentage of fleets is so mixed that significant quantities of both oil categories are needed. My experience is that nowadays the only gasoline-fueled engines in a major fleet might be a few pickups and passenger cars. Does it make sense for this 1 percent of the applications to control the 99 percent?

For now, negotiations continue between the players. Something has to give and whether it is total extinction or a smaller place in the market, universal oils will not go quietly. There is probably an asteroid or comet out there with uni-versal oils written on it, waiting for its chance.

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