Mineral oil is definitely for R-12. This compressor is probably new old stock (NOS). Ester or PAG are the oil choices for R-134A. I occasionally have memory lapses so confirm the ester oils are often used for conversions as they are more compatible with left over mineral oil from R-12 systems. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of J Stewart
Sent: Sunday, July 08, 2012 10:14 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: I lost my cool!!

Then, if that is true, the compressor Bus Depot just sold me as compatible with either R12 or R134A isn't-the label on it says "mineral oil" I'm still confused here and don't want to ruin an expensive part! Jeff Stewart ----- Original Message -----
> On 7/8/2012 9:05 PM, Dave Mcneely wrote:
> > Hmmm..... . The AC Pro stuff I saw today at AutoZone is R134a. The 
> > fittings for R134a and R12 are different of course. If your vehicle 
> > has not been converted, it is R12.
> Good catch. R134a systems are required by law to have different 
> fittings, which would point to it being an unconverted R12 system.
> R134a
> requires a different lubricant (PAG or ester), because it won't 
> effectively carry the R12 lubricant (mineral oil) through the system.
> The result is a ruined compressor.