Unlikely that it's a road thing.

Oily substances are used in a variety of places. The aerodynamics of
your vehicle is such that anything spewing oil is likely to have it end
up on the back hatch.

So. Your next set of choices are, what type of oil is it? Is it gummy?
Is it very thin? Is it dark? Is it clear?

Do you have power steering? I leak on the high pressure side could come
out in a mist that could get sucked into the windstream. Same is true
of your AC system, if you have one.

Is your engine oily? Yes? Then get some brake cleaner and spray it on
(when your engine cold) and get all that oily stuff off. That will make
diagnosis easier. I assume since you haven't found the oil source, that
your engine is not oily. The next easiest thing I'd check would be the
AC lines (if you have AC). These run up behind the cabinets. Since the
film is on the outside, I'd say, check the lines under the van towards
the receiver dryer (in the left rear wheel well).

If the oil residue is heavier on one side than the other, that could
help, as the AC lines run on the LEFT side, but the Power Steering
lines run on the RIGHT side.

With a 18 year old vehicle, it would be a good time to look at those
(metal) power steering lines that run up to the front. They can rust
through.

On Nov 6, 2005, at 11:56 PM, BA wrote:

> Hi, all,
>
> This was discussed once (as far as I could find) in the archive, last
> August.  The sole response to the described problem was "look under
> the engine ... if it's sufficient to put an oily film on your back
> hatch, the cause will be obvious".
>
> Except ... it's not obvious!  Not to us, nor to the VW repair shop
> where we take our Vanagon.  And the repair shop has so far not steered
> us wrong. (Our shop-supplied engine has not yet done 10,000 miles. And
> it isn't a re-conditioned engine ... it's a new VW engine.)
>