I have been using Mobil 1 oil, 0W-40 grade, in my '96 2.4 Diesel
Transporter, almost since new. Originally, this oil satisfied
VW specs 500.00 and 505.00, as recommended in the handbook for
this vehicle.

Over the last few years, formulations of this oil claim testing
to VW 502.00, 503.01 and 505.00. I understand that 502.00
supercedes 500.00, and that 503.01 relates to longer drain
intervals with "smart monitoring" of driving patterns.

Interestingly, I came across a web site which claims that this
newer formulation must _not_ be used in pre-2000 vehicles, such
as mine. According to a discussion at http://tinyurl.com/d9ph3

"Note: Engine oils according to VW standards 503 00, 503 01, 506
00 and 506 01 must not be filled in vehicles up to model year
2000 (Y). " and "Elsewhere in VW literature it states using
50300, 50301 oils can cause engine damage in engines they are
not recommended for. ie pre 2001"

Most 0W-40 grade oils these days seem to include VW 503.01.
Google doesn't pull up any confirmation of this claim. Can
anyone cast more light on this, and/or any possible reasons why
it would be so?

John