We have 4 parts stores in the town I live in (8000 people), the one I use, It was a family owned store,
that has been here since the 1960's, there is only one family member remaining, he has been there for
over 40 years. You walk in tell him what you need and what vehicle it's for and he just goes and gets
the part, very seldom goes to the computer to look it up.
He is the only parts store guy, that I will even consider taking advice from.
Sadly he is retiring next month, he's 70 though and hes earned it.

 

The oil in the system gets mixed with the freon. If the ac was off and not used the oil goes down to the bottom of where ever it is. I had a leaky evaporator coil and the oil was dripping out of the water drain at the lower firewall. If you don't see oil over everything then hardly any escaped. If you do replace the receiver drier(as you should since the system was opened up) you need to take that in to account for how much oil to put in.

 

Thanks for the info on the oil part of this. The line sprayed pretty hard ...seems like it could have been a bit oily (unless Freon has some of that characteristic too?), but i didn't really pay that close attention. was too busy playing with my heater core.