I believe your low sulfer diesel in the US is 10ppm, ours here is 5ppm. Heating oil is like 500ppm, and standard diesel (also called winter diesel) is 50ppm.
You could get away with a tank of 50ppm but as BMW has up'ed the power of there diesel engines the better the diesel fuel is required.
I believe Europe in now down to 1 or 2ppm, this is also partly why the US only gets the 35d and not the 40d, as the power is ramped up it requires a cleaner fuel. Its also makes it harder to meet the emission limits with 10ppm.
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