my father in law(the audi and bmw owner) was so baffled by the whole diesel fuel difference theory. that today he rang his usual audi dealer - audi manchester, to discuss, he also was wondering what 'nicht fur biodiesel' menat inside his fuel filler cap(i know its pretty obvious but..) he wondered whether it meant - don't used full B30 biodiesel(30% bio mix) or not to use a bio mix(morrissons 7%) their comments shocked him 'don't go anyway near a petrol station that sells diesel with a hint of biodiesel as it is causing our customers massive problems'
after a conversation, it seemed that it was the later cars that were having more trouble than the older cars.
Their explaination was that the newer cars, were using injection pressures greater than ever, so that the fuel atomises more, and therefore combusts better. the biodiesel, is more viscous and has zero detergent levels, as the commonly used detergents cannot bind with biodiesel. therefore the injectors and fuel pump etc were working overtime.
now, 7% doesn't sound a lot, but thats 7 litres of refined chip fat in your tank every 100 litres purchased. so approx 4.5 litres(or about a gallon) every average 65 litre tank in an alfa.
i have heard enough, and have had enough experience now to believe that there is a difference between fuels. So i will be sticking with standard forecourt fuel from the big boys.
chrisyounguk - glad you have finally got to the bottom of yours! keep us updated.
i will let you know how mine gets on with the new parts fitted.