I've had my 84 tin top with a westie interior now for over 60k miles.  It
has an inline gas vw motor, mounted using the factory diesel engine set up
and a 5sp manual trans from a diesel vanagon.
  I've just been looking at the Fuelly app I began using in September,
tracking all my gas  consumption with a smartphone... Even including some
two weeks with no oxygen sensor operating and over 44 fill-ups I have an
average gas mileage of 25.5 mpg.  Those who might have doubt's or even some
interest in checking their Vanagons against those who've recorded on the
Fuelly site can google it and search the vanagons ...

  In the appx. 3 mos. since I started with Fuelly I've logged about
10,500mi. which Fuelly says I paid for at $.13 cents/mi.  My best tank was
27 mpg. +

  Not bad for a used 93 Jetta block with a 92 rabbit head stuck on
top...The motor cost me $300 but I did replace some stuff, bringing my cost
for this 60k mile(so far) motor to $600.

  I ain't sayin this is what everyone should do for Vanagon
motors....Whatever turns your wheels....Just putting out MY experience with
this often pooh poohed engine for the vanagon.