Mercedes Tightens Oil Specs


STUTTGART, Germany – Mercedes-Benz has adopted a wide-ranging upgrade of service-fill engine oil specifications for its passenger cars and heavy-duty trucks. The standards, which were unveiled here at the Uniti Mineral Oil Technology Conference on March 21, feature new or tougher requirements for fuel economy, compatibility with biofuels, cold and high temperature performance and protection from wear.

The automaker acknowledged that the addition of several new tests will increase costs for formulators attempting to qualify engine oils.

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I think we have never before had so many new tests, Michael Schenk, manager, automotive lubricants here with Mercedes-Benz parent company Daimler AG, told the conference. But we are facing a number of challenges both now and in the future, and we need to address them.

The upgrade, named V2012.1, is actually an update of a collection of specifications for standard, medium and top quality oils with standard and low ash levels for passenger cars and heavy-duty trucks.

Schenk said Mercedes-Benzs biggest priority in upgrading the specifications was to demand that engine oils help its vehicles meet aggressive European Union targets for improving fuel economy in order to reduce carbon dioxide emissions. European automakers face large cash penalties in coming years if they do not meet mandates capping CO2 emissions.

To move toward those goals, the company introduced four new chassis dynamometer tests for passenger cars, each with a different engine that corresponds to different Mercedes-Benz vehicles and all adhering to the New European Driving Cycle. For heavy-duty engine oils, the company modified a test run on its existing OM 501 LA engine so that it now completes the World Harmonized Transient Cycle, a driving conditions simulation developed by the United Nations.

Fuel economy will be the most important for us, Schenk said. The emissions targets set by the EU are going to be very challenging for us, so we need to continue working toward them.

Biofuels was another major focus of the upgrade. Unlike conventional petroleum fuels, the industry has found that fuels made from plant oils tend to accumulate in engine sumps, thus diluting engine oils. Automakers are concerned that lubricant performance could be compromised in a variety of ways, especially in light of calls to increase the use of biofuels.

V2012.1 includes one new 168-hour bench test developed by Daimler to measure an oils ability to fight oxidation and maintain viscosity in the face of higher dilution by biofuels. Conducted in a 500 milliliter three-necked flask, this test is conducted on samples consisting of 95 percent candidate lubricant and 5 percent B100 biofuel.

If you add 5 percent fatty acid methyl ester biofuel (to an oil sump), you will have a dramatic increase in the oxidation of that oil, Schenk said.

Daimler also modified an existing test for corrosion inhibition at high temperatures to account for biofuel dilution. According to Schenk, corrosion of lead, copper and tin can all increase significantly when engine oils are diluted with biofuels. Daimler modified the existing High Temperature Corrosion Bench Test (ASTM D6594) to require candidate oils be diluted with 10 percent biofuel.

Perhaps the most important biofuel test is not yet completed. Mercedes-Benz, other automakers and representatives of oil and lubricant additive companies are working together through the Coordinating European Council for the Development of Performance Tests for Fuels, Lubricants and Other Fluids (CEC) to develop a single new test of the effects that biodiesel has on four oil performance parameters: piston cleanliness; ring sticking; formation of oil sludge; and oil degradation. The test will be run on a Mercedes-Benz OM 646 DE22 LA four-cylinder 2.2-liter diesel engine, but work continues and may go on for some time.

The biodiesel effects test is one of the most important tests for the whole industry, he said. Unfortunately, it is not ready. It is difficult to predict when it will be ready. I think the test development group needs more time and more money. Whenever it is completed, this test will be incorporated into V2012.1, he added.

The upgrade is also awaiting completion of a CEC bench test for low-temperature pumpability of aged oils. Such a test became a priority for European automakers after a rash of engine failures suffered in Europe during an extreme cold spate in the winter of 2008-2009. The failures were attributed to engine oils that turned to gel.

Schenk said the CEC has nearly completed its test, currently dubbed CEC TDG-L 105, and that Mercedes-Benz will incorporate it into its new specification once it is finished. This two-part test begins with ageing the oil in the presence of biodiesel, and then using a mini-rotary viscometer to evaluate its low-temperature pumping performance.

The new specifications also include a new bench test for protection of aluminum-silicon cylinder liners; and stricter requirements for cam wear, creation of engine sludge and piston cleanliness.

Schenk acknowledged that the new tests will increase qualification costs but maintained that Daimler had reduced the impact by developing some as lab and bench tests, rather than relying on costlier engine sequence tests.

The impact of the V2012.1 will be blunted by Daimlers schedule for phasing it in. Oil marketers will still be able to qualify oils to the previous specification for one year. Those obtaining such approval will have permission to label their products as meeting Mercedes-Benz requirements for five years after approval.

Schenk said specification writers – and the lubricants industry – will have more work to do in the future. Daimler has already begun work on the next Mercedes-Benz upgrade. One of the priorities for that update will be to require that oils be thinner in order to further improve fuel economy.

Its clear, with the next specification we will have to go to lower viscosity, he said.