I don't actually drive a Vanagondiesel, but between my '70Kombi and my 
'92 JettaEcodiesel, I may be able to help.

According to Chevron,

Diesel #1 is a winterized fuel, and as thin as diesel gets.  Usually only 
sold during the winter and/or up north.  

Diesel #2 is your standard truck/auto diesel.  Normally, this is sold 
spring/summer/fall and then replaced with #1 for the winter; however, 
some dealers in southern climes simply sell a winterized #2.

Diesel #3 and #4 I believe are only for tractors and other 
farm/industrial equipment.  

I asked the local truck-stop guy, and he said, "It's winterized after 
mid-November."  #1 or #2, He/I didn't know.  To be extra-sure, I add some 
"Diesel Fuel Supplement" at every tankful and have had no problems, even 
in -10 degree weather (with block heater plugged in).
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>From what I understand, diesel is a less-refined version than gasoline, 
requiring less processing because of its "crudity."  Cost-wise, I've 
heard that gas companies are gouging us diesel owners by not charging a 
cost relative to the lesser degree of processing, but............

On Thu, 1 Dec 1994, Stuart Hutton wrote:

> Hello vanagonites,
> Does anyone know of the recipe for diesel #1.  My wife, actually  asked it
> in that way after my brake fluid feast.  Our vanagon seems to really prefer
> to run on diesel #1, the milage is higher, starting is much easier, etc.
> However, unless it's 14 below here, we can only get diesel #1 by driving
> a long ways (140 miles round trip).
> Also, if anyone has great knowledge about diesel in general (the fuel)
> i would like to know what type of process produces diesel.  What makes
> diesel ultimately cheaper than gasoline?
> Thanks,
> Stuart
>