How do I add 134A and PAG oil to my A/C in my '05 S80? I do see that our local auto parts store sells just 134A, and also 134A with PAG oil.

Any suggestions, advice? Also, how much PAG oil does the A/C need (ratio of 134A to PAG). I do realize the system uses 2.2Lb of R134a.

Thank you.