The ACEA 2012 engine oil sequences, adopted in December by the European Automobile Manufacturers Association (ACEA), introduced a test of used oil pump-ability at very cold temperatures, aiming to prevent any repeat of a surprising rash of engine failures four winters ago. Another new test measures whether oils can maintain performance even when diluted by biofuels.

Cold-temperature pumpability and biofuel dilution have been big concerns for the industry the past few years. The pumpability issue arose in the winter of 2008-2009 when numerous engines were destroyed during a severe cold spell in Europe. Automakers concluded that crank-case oils had turned to gel while vehicles sat, and then could not be pumped and circulated once engines were started. Starved for lubrication, the engines seized.

ACEAs oil specifications already included a test meant to ensure that oils remained pumpable at low temperatures. It called for cooling fresh oil – to a temperature ranging from minus 15 to minus 40 degrees C, depending on oil grade – and then slowly stirring with the paddle of a mini-rotary viscometer.

After the rash of engine failures, automakers decided the existing MRV test did not provide enough protection and that they needed to test whether an oil maintains its pumpability in use, especially as it is diluted with biodiesel.

The MRV test on fresh engine oil has now been shown to be an insufficient test to demonstrate durable low-temperature pumpability performance during OEM oil drain intervals, particularly in the presence of biodiesel, said Adrian Fitzpatrick, technical manager in the Engine Oils Group at additive supplier Lubrizol.

The new test, dubbed CEC L-105, begins by diluting a sample of fresh oil with 5 percent biodiesel, then simulates aging by heating it at 150 degrees for a prescribed period of time. The sample is then cooled and its viscosity measured as in the older MRV test. The new test is a requirement for all four E classes of oil (for heavy-duty diesel trucks), all four C classes (for diesel-powered, light-duty vehicles) and for three of the four A/B classes (for gasoline-powered, light-duty vehicles).

An official at Swedish automaker Volvo said a new cold-temperature test was something truck manufacturers felt they could not do without.

The failure mode [for the incidents in the winter of 2008-2009] was catastrophic – it resulted in engine seizures – so the test is vital, said Bengt Otterholm, lubricants coordinator for Volvo Technology, who also is chairman of heavy-duty oil sequence development for ACEA. Even though the oil and additive industries may have figured out what caused the problem, we cannot be certain it wont happen again. If we have the test, we can hopefully avoid this happening again with another bad combination of additives and base oils that doesnt get tested.

The biodiesel problem stems from the fact that most of Europes diesel now contains a portion of fuel derived from plant oils. One unintentional side effect of modern fuel combustion technologies is that it is easier for uncombusted fuel – both conventional and bio components – to migrate to crankcase oil sumps. Conventional diesel tends to burn off there, but biodiesel does not, and so it collects. Some studies have found biodiesel content in engine oils reaching upwards of 20 percent.

Not surprisingly, dilution inhibits engine oil performance, including its durability and ability to protect components from wear. So for the first time, ACEAs 2012 sequences include a lubricant test involving biodiesel – GFC-Lu-43A-11, which was developed by GFC (the French Coordinating Group for the Development of Performance Tests for Fuels, Lubricants and Other Transport Fluids). This test dilutes engine oil samples with B10 (diesel containing 10 percent biodiesel), then mixes is with air at 170 degrees. After a prescribed period of time, the sample is checked for degradation. The test is now part of the sequences for all C classes and the A5/B5 class.

ACEAs engine oil sequences usually use tests developed within the framework of the CEC (the Coordinating European Council for the Development of Performance Tests for Fuels, Lubricants and Other Fluids), an umbrella organization for testing groups in individual Europe-an countries, including GFC. In this case, ACEA used the GFC test out of convenience.

The GFC test was the only method in existence to test an oils ability to withstand dilution by biofuels, said Sebastien Vautier, technical manager for automotive lubricants at PSA Peugot Citroen. The CEC did not have time to develop its own test, so [ACEA] used GFCs. The CEC still plans to develop a test of its own to replace the GFC method.

In addition to the pumpability and biodiesel tests, the 2012 sequences contain several other changes, in-cluding:

tougher limits in the A1/B1 category for Noack volatility, wear (on the OM646LA test) and piston cleanliness (VW TDI test);

introduction of piston merit and sludge limits for the A3/B4, A5/ B5, C3 and C4 classes;

the new sequences no longer allow formulation applicants to use grandfathered results from the Daimler M111E sludge test instead of the new Daimler M271 sludge test.

An official at additive supplier Afton Chemical said that the new requirements, taken individually, are not much harder than those in the previous sequences, ACEA 2010. But it is significantly more difficult, they added, to formulate oils that meet all of the requirements.

Generally, it is the details of the specification, additional parameters and additional bench tests adding to the overall complexity of the specification, although in isolation any one of the changes is not apparently so significant, said Harvey Watson, Afton marketing manager for passenger car motor oils in Europe, the Middle East and Africa.

It may be too early to know if existing engine oils will require much reformulation to comply with the upgraded specifications.

On the basis of extensive pre-work, we are confident that the majority of our passenger car formulations will pass the new tests, Lubrizols Fitzpatrick said. But there are many formulations to test, and this, along with associated documentation, will require significant investment.

Asked about the need for reformulation, Watson said, That depends upon how well organizations built future capability into the ACEA 2010 products.

Although the new sequences are available for use, the previous specification will be phased out over a two-year period. Until 13 December 2013, oil marketers may continue obtaining approvals for products that comply with ACEA 2010. After that date, marketers will be able to file new claims only for oils meeting the 2012 requirements, but they may continue selling any previously registered oils and promote them as complying with ACEA standards for another year. After 22 December 2014, only products complying with ACEA 2012 should be marketed as complying with the organizations standards.