I’ve got a Golf III Variant 66 Kw / 90 PS Bj. 1995 I believe with a Bosch VP37 fuel tank? The problem is the diesel and biodiesel or fuel oil is not 100% the same. With biodiesel the lubrication properties are not supposed to be do good. Heating oil is colored red, it is deflated and because it has reduced lubrication properties. I have heard up to now various things how to mix fuel oil so that the fuel pump does not break, but I don’t know which is right. – By adding additives the problem should be solved with the lubrication, but no idea if that’s true. – Some say 5% biodiesel should be mixed with the fuel oil, but that’s unlikely The problem is that biodiesel alone apparently already fulfills these properties 100%y, so that a pump can wear away faster? In addition, you don’t have to let the biodiesel pass away at low temperatures.