[Vwdiesel] Air-cooled and diesel oil?

[Mary Beth and Chris Geiser]

A question for the list oil guru's and anyone familiar with VW's
air-cooled engines (since diesel guys generally know lots about
everything - and we're better looking)...

The great majority of my miles get put on my VW diesels ('92 Ecodiesel,
'82 Vanagon), but I have a '74 Westy (air-cooled) that we camp with in
the summer (which in recent years in Wisconsin seems like about a
month).  40W oil is recommended for the Westy... are there any issues
with using the 15W40 diesel rated dino oil (Cenex) in the air-cooled gas
engine?  

I keep enough of the diesel oil around - just seeing if I can avoid
having to keep a whole supply of different oil just for one rarely used
vehicle.

Thanks,

Chris