So I just read some rather disheartening things about this new TDI.
http://www.biodieselmagazine.com/article.jsp?article_id=2290&q=&page=1
http://forums.tdiclub.com/showpost.php?p=2460347&postcount=393
http://www.dieselgreenfuels.com/chevron_dpf.pdf
The summary here is that the way VW implemented its new emissions system means that the engine cannot (or should not) be fed high concentrations of bio-diesel! VW is saying that the maximum ratio should be 5% bio, or B5.
Apparently the engine injects unburned fuel into the combustion chamber on the exhaust stroke. This fuel is then carried into the exhaust and 'burns' the particles trapped in the 'diesel particulate filter' or DPF. This DPF is the magic gadget that lets the new TDI's meet the new emissions rules. Unfortunately when they do this some fuel gets into the crankcase and contaminates the engine oil. Petroleum diesel can be tolerated for various reasons, but bio cannot.
I think it is clear that this is likely why VW mandates a special, rather exotic synthetic oil as well. This oil is probably more tolerant of having fuel mixed into the crankcase.
Older TDIs do not have this problem because they never inject diesel into the combustion chamber on the exhaust stroke.
Starting to feel that this emissions system is quite bleeding edge and an unknown quantity. Maybe I should just stick w/ gas, just like everyone else.
From the Chevron presentation:
Diesel fuel price and exhaust after-treatment differential presents the
most significant barrier for light duty diesel engines in US vehicles
I'll say..
