Efforts have coalesced to develop a method to assess cold-temperature performance after an oil has been in use. Those working on the project say the industry should have its test by next winter.

Automakers have been reluctant to provide specific details about the engine failures from two years ago. Observers say original equipment manufacturers generally avoid disclosing such information, either out of fear that it could tarnish their reputations or that it could compromise their handling of warranty claims.

LubesnGreases gathered some information from sources involved in inter-industry discussions of the problem and through documents from several companies that last year were temporarily posted on the website of the Coordinating European Council for the Development of Performance Tests for Fuels, Lubricants and Other Fluids, better known as CEC. Sources said at least three automakers reported engine failures in passenger cars and heavy-duty on-road trucks. Those engines appeared to have been damaged, they said, after their lubricants underwent gelation, a phenomenon in which lubricants exposed to extremely cold temperatures take on a gel structure that prevents them from circulating.

One of the presentations posted on the CEC website, by Infineum, relayed information provided by one of the automakers. An unspecified number of that automakers engines failed after overnight temperatures – it was unclear whether these failures occurred on one or more calendar days – reached between minus 20 and minus 25 degrees C. The vehicles started afterward but ran for only one to three minutes before main and connecting rod bearings were destroyed because of insufficient lubrication. Upon inspection, their engine oils were found to be firm enough to cut, Infineum stated.

The industry has witnessed other spates of engine oil gelation on a few rare occasions over the decades. As a result, engine oil specifications include cold-temperature pumpability tests. Performed on mini-rotary viscometers, these procedures lower oil temperatures at controlled rates to set levels – usually between minus 10 and minus 40 degrees C. The MRV then turns a calibrated rotor through the oil and measures its viscosity and checks for yield stress.

But there is growing consensus now that existing test methods have an important shortcoming. Specifications call for them to be run on fresh samples of candidate oils, and so they only speak to the cold-temperature performance of the oils when fresh. Those studying the engine failures of 2008-2009 say that lubricants can lose their cold-temperature performance as they age in the crank-case. Moreover, they worry that industry trends may be accelerating the speed with which that happens. Probably the most concerning trend is the growing use of biodiesels and their dilution of engine oils. In an effort to reduce dependence on fossil fuels and to support renewable products, European governments have mandated that diesel contain minimum amounts of fuels made from plants – usually seed oils.

At the same time, original equipment manufacturers have employed fuel spray patterns and piston wall impingement methods that inadvertently allow uncombusted fuel to get past piston rings and be scraped into the oil sump. This migration includes both conventional and biodiesel, but the former is volatile enough that it evaporates. Biodiesel is less volatile, so it remains in the sump and builds up over time.

Technical experts have concluded that dilution by biodiesel can compromise an engine oils ability to avoid gelling at cold temperatures. They believe the same can result from accumulation of soot, a trend resulting from adoption of emission control technologies such as exhaust gas recirculation. Other detriments are oxidation and nitration, effects of engine oil aging.

It is probably no surprise that changes to the chemical nature of engine oils can affect their cold-temperature performance. But industry players have expressed some alarm at how quickly this can happen.

Analysis of the failing oils shows that, while obviously used, they were not excessively degraded, with only mild oxidation, nitration and low [acid levels], low levels of soot and limited fuel dilution, Brussels-based CEC said in another of the documents on its website. Yet most oils that meet specifications do not gel, the organization noted, suggesting that formulation is also an important factor.

Infineum, an additive supplier head-quartered in Abingdon, U.K., said it conducted extensive tests on cold-temperature pumpability of aged oils and that its findings bolstered those observations. In field trials on passenger cars and heavy-duty trucks, some oils held their cold-temperature pumpability while performance of others deteriorated in less than 20,000 kilometers. In the truck trials, some oils that passed pumpability tests when fresh failed within 16,000 km.

Fresh oil performance is no guarantee of performance in the aged oils, concluded Infineum Crankcase Specialist Danesh Golberdhan, author of the companys presentation. Oils with mi-nor formulation changes can give either excellent or very poor low-temperature pumpability performance very early in the mileage accumulation.

In light of these findings, many in the industry agree that it needs new tests to measure the cold-temperature pump-ability of oils after theyve entered the crankcase.

There is currently no test in Europe assessing the low-temperature pump-ability of aged oil in the presence of fuel dilution, said Emmanuelle Faure-Birchem, Chevron Oronites product line manager for automotive engine oils in Europe, Africa and the Middle East. Development of this test will help close this gap and thus prevent potential field issues.

For the oil companies and OEMs it is really a significant concern, said Laurent Tiquet, chairman of the Engine Lubricants Technical Committee for the French Coordination Association for the Development of Performance Tests for Transportation Fuels, Lubricants and Other Fluids. GFC is CECs counterpart in France. It is the biggest priority at the moment. OEMs that had to deal with claims for failed engines are motivated by that. Other companies are concerned that numbers of failures could rise.

Several companies and organizations have undertaken to develop test procedures to address the problem. Daimler developed its own procedure, of which Oronite and Infineum developed modified versions. GFC developed a procedure contributed by member Peugot and was on the verge of adopting it when work was halted in October. Infineum also did some work to modify the GFC method.

Now all of those efforts have been subsumed into a test development exercise by CEC. The organization announced the formation of a test development group last fall after the need for a procedure was endorsed by ACEA (the European Automobile Manufacturers Association), ATIEL (the Technical Association of the European Lubricants Industry) and ATC (the Technical Committee of Petroleum Additive Manufacturers in Europe). CEC selected Salbergen, Germany-based ISP to be the lead laboratory for the initiative and selected 10 oil and additive companies to be on the test development group. Its first meeting was scheduled for mid-December, and the CEC said it hoped to complete the work during the second quarter of 2011.

Automakers and oil companies are determined that the new procedure will be a bench test rather than an engine test, which would cost far more in terms of both time and money. Judging from the work done to date, the new procedure will probably use a mini-rotary viscometer, but the key will be to devise a method to simulate the aging process.

The methods proposed so far have tried to accomplish this by subjecting oil samples to heat and blown air for varying periods of time ranging up to several days. Daimler and GFC both believed their procedures adequate, at least at some point. But Infineum and Oronite contended that both those procedures were too severe, that they would cause too much simulated aging. Critics say the method should identify oils that become gelation threats much earlier on.

It is known that the procedures used in the current GFC and Daimler tests are too severe, CEC said. They produce oils that are much more heavily degraded (especially for oxidation) than oils which have failed in the field, and they do not give results that are in line with known or expected field performance.

The methods discussed so far have taken the same general approach. For example, Oronites called for a 250 gram sample of oil diluted by 10 percent with B7 biofuel. The sample would be aged at 160 degrees C for 48 hours in Daimler glassware. Temperatures for viscometer readings would range from minus 20 to minus 30 degrees C depending on the viscosity of the oil. Oronite said its pro-cedure has good correlation with field performance.

Infineum said it improved the Daimler procedure by shortening the aging simulation to 72 hours, and by using a different type of biodiesel.

CEC emphasized the importance of developing a test that can be shown to discriminate between oils that when aged and diluted with biofuel are likely to gel at cold temperatures and those that are not. In an apparent nod to the difficulty of this task, the organization posed the possibility that it will not succeed.

In the event that no discrimination between the calibration oils is achieved, all work should be put on hold pending a full review by [CECs] Managing Board to decide whether to terminate the project.

If the test development group does find a procedure that can discriminate, the question will be how much of an impact will this have on the oil market. How many oils that meet current specifications will fail the new test? Those that do would presumably require reformulation if companies want to continue marketing them in the same way.

ATIEL predicted that the impact will not be very large.

Based on the limited data presented by ACEA, the issue appears to be isolated, the associations Industry Liason Group stated in response to questions. Nevertheless we support continuous improvement of industry engine oil specifications.

Oronites Faure-Birchem maintained that it is too early to know.

Until the test method and specifications are agreed upon, it is impossible to judge the impact of any specific oils.

European automakers will be crossing their fingers for two reasons this winter. First theyll wish to avoid a repeat of 2008-2009 while they still lack an accepted test for cold-temperature pump-ability of aged oils. Second, theyll hope that the CECs new test will protect them from such problems in the future.