Tonight I have just finished making an oil pan that will allow an ALH engine to run at 50 degrees (VW Vanagon application). My aluminium welding is getting fantastic when I weld stuff like 6061 aluminium. The filler rod that I am using is 5351 and my Miller Syncrowave 180 is of course on AC and biased around 7 to 8 for most welds that I do. With that setting I can get the very nice ripple effect that everyone thinks is so nice and the weld quality/penetration on 2 to 3mm thick aluminium is great - Best Flux Core Welder that is on commercially purchased aluminium. The instant I start welding on a Volkswagen oil pan or intake manifold I get all these little black flecks in the material and the welds turn out pretty crappy - it just doesn't flow worth a darn almost a crust on it when it is molten. Everything is cleaned with brake cleaner and then I scrub the heck out of it with a stainless brush to ensure that it is clean clean clean... Does anyone have an idea of what the alloy of aluminium Volkswagen is using?