As part of their efforts to reduce dependence on petroleum, developed countries have for roughly a decade required gasoline and diesel to be supplemented with fuels from renewable resources. To gasoline fuel suppliers add ethanol, which is made when a starch- or sugar-based feedstock undergoes fermentation. Diesel is mixed with biodiesel, fatty acid methyl esters (FAME) produced when vegetable oils are combined with methanol in a transesterification process.

The current convention is diesel with 7 percent FAME – referred to as B7 – and gasoline with 5 percent bioethanol, or E5.

At some point it became apparent that the biofuels were entering engine oil sumps and accumulating there – sometimes to the point that the engine oil was significantly diluted. As Abdelhalim explained, this can interfere with lubricant performance in several ways. Biodiesel causes the oil to thin, thereby reducing its protection against wear. It also reduces additive performance, causes the oil to degrade faster and reacts aggressively with some seals. Ethanol also speeds oil degradation and facilitates formation of water, leading to corrosion.

Industry is working hard to develop procedures that can identify oils capable of standing up to biofuel dilution. The CEC (Coordinating European Council for Development of Performance Tests for Fuels, Lubricants and Other Fluids) is working on at least four tests. One of its test development groups recently finished writing a test for cold temperature pumpability of engine oils diluted with biofuel. Expected to be adopted by January, it will be the first CEC engine oil test to include biofuel. Another CEC group has been working for two years on a test to gauge a diluted oils ability to prevent formation of sludge and deposits.

However, the test group struggled to develop a test that could address both failure modes, as deposits and sludge were formed under different conditions, said Abdelhalim, who is based in the United Kingdom. As a result, it is starting over and will now focus on deposits.

In October the CEC invited tenders for sponsors and a lead laboratory to develop a third test – this one for oxidation stability in the presence of biofuel. Abdelhalim also noted that a European automaker has developed a procedure to test the capability of oils diluted by bioethanol to protect against deposits on turbochargers. The CEC has indicated it would like to consider this test for inclusion in ACEAs oil sequences, and the organization is preparing round robin tests to assess its reliability and repeatability. If approved, it will be the first ACEA engine oil test that involves bioethanol.

As Abdelhalim said, these tests have not been easy to develop. Automakers originally wanted to include a cold temperature pumpability test by the second quarter of 2011. When it was unable to finish that quickly, some automakers incorporated a test developed by GFC, CECs member organization in France. Once the new CEC test is formally adopted, she said, those OEMs will probably switch from the GFC test.

Abdelhalim expressed confidence that CEC will ultimately succeed in writing tests that reliably distinguish between engine oils that can still perform when diluted with biodiesel and those that cannot. She added that formulators have ways to cope with existing dilution levels, although some risk sacrifices in some oil performance parameters. Increasing dosage of antioxidant additives can stave off degradation, she said, although formulators need to use phenols or amines, which are effective against FAME. Detergents can neutralize the acids formed by FAME and degradation, but careful selection is again needed. Dispersants can help prevent formation of sludge but may detract from fuel economy, Abdelhalim said. Moreover, the risk of dilution in general may limit opportunity for low-viscosity oils that could improve fuel economy.

Abdelhalim suggested that there is a limit to the amount of biofuel dilution that oils can tolerate. She noted that the EU has adopted a goal that 10 percent of transport fuels come from renewable resources by 2020. To meet that target, the region could move to two diesel grades – B7 and B10. B10 would probably increase dilution levels in oil sumps, she said.

ACEA (the European Association of Automobile Manufacturers) has urged the EU to consider alternatives, such as mandating use of renewable fuels in other modes of transportation.

E10 and B7 will contribute significantly to meeting the 10 percent target, Abdelhalim said, but there are valid alternatives to achieving the target other than simply escalating the blending of biofuels at levels beyond E10 and B7.