I'd try the 80% first, but let the high side pressure be the determining
factor.  Check your Bentley; there is a switch that speeds up the
radiator fan when that pressure gets above 210 psi.  Add refrigerant
slowly with the AC turned to max and the engine running 1500 rpm or so,
until the fan goes to the higher speed and back down and the high side
pressure cycles at around 200.

Since the system has been open, you should pull a full vacuum for at
least an hour before charging; don't let any air back in.

I assume your using ester oil which will dissolve any remaining mineral
oil.  I believe that I used about 5 oz, putting about 1 oz of that in my
new accumulator.

good luck,
 Larry A.
91 GL which leaks about 1 can of 134a per year

Barry Rokusek wrote:
>
> Hey.  I'm sorry to be so dramatic, but I'm meeting the mechanic Thursday
> evening to charge up my AC.  And I still don't know how much I R134a and lube
> to use...  I've changed o-rings, dryer....  VW says 47.6 ounces and 5.8 of
> lube.  That's about 94% of what the R-12 was.  Others say 80%.  I have an 86
> Westy with the Sanden 508 compressor.  I'd really appreciate any advice!
>
> Thanks,
>
> Barry
>
> Madison, WI