I am new to the world of diesel engines and was wondering if there is a difference in quality between stations. Would it be better to purchase from a place such as Shell, Exxon/Mobile or the QT/Race Track type places.

Due to geographic location, We get our fuel from either Alberta and BC or Alaska.
I find the fuel from Alaska provides around 100kms more range in a number of alternate testing patterns. Out of the ground it is a better quality/purity than the Canadian refineries process.

I suggest you try a few different dealers to find what works best for your engine.

Ashleey, who lives in Ireland but is British and returns regularly says there is a difference in the two countries and recommends "Shell V Power or the BP Ultimate" or additives.
The issue of cold start being raised by v6tdi (in Haiti) is as yet unresolved so please post any findings you make with respect to quality.<ul><li><a href="http://forums.audiworld.com/q7/threads/4754.phtml#30582">link to Q7 forum thread</a></li></ul>