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Diesel as a fuel is changing: Part 2 of 3

Diesel as a fuel is changing: Part 2 of 3

Biodiesel in pure form requires certain measures

biodieselAll in all, biodiesel reduces CO2 emissions by around 50 percent. It is free from sulphur and aromatics, and biologically degradable. In high concentrations the reverse side of the coin is incompatibility with some plastics and rubber, poor low-temperature performance, an inadequate shelf life and higher nitrogen oxide emissions during combustion. Some fleets have even gone beyond biodiesel as an admixture, and are refuelling their vehicles with pure biodiesel to save costs, how­ever owing to the limitations of biodiesel this is not possible unreservedly.

All Mercedes-Benz commercial vehicles have been approved for biodiesel since 1988, though initially with the proviso of shorter oil-change intervals. New Mer­cedes-Benz trucks and buses are optionally available with extra equipment for bio­diesel, and retrofitting is possible for vehicles already in operation. With a pack­age consisting of modified unit pumps for the fuel injection system, a fuel pre-filter with a heated water separator and an auxiliary tank for conventional diesel fuel to ope­rate the auxiliary heater, oil-change intervals are now approaching those for en­gines with conventio­nal diesel fuel. And not least, the operating life of the auxiliary heater is maintained thanks to operation with conventional diesel fuel.

Using biodiesel is not possible in vehicles with an EEV emissions classification, as biodiesel generates up to 20% more nitrogen oxide emissions than diesel fuel based on mineral oil.

The use of non-estered, practically unprocessed vegetable oils in commercial ve­hicles is definitely not recommended. This raw material for biodiesel is subject to inadequate checks and causes damage to valves, injection nozzles, pistons and piston rings. There is also a risk of oil dilution and partial breakdown of the engine oil, with potentially serious consequential damage.

Daimler, Ulta Leitner, 2015

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