The A/C in this car uses PAG150 oil, doesn't it?
 

I was looking in the factory service manual last night for my 1999 Alero. All it says is to use PAG oil, which implies PAG46. Various places on the internet suggest either PAG150 or PAG46, depending upon where you look. But mostly PAG150 (I think the 4 cylinder Alero does use PAG46).

This might very by year and engine, so can anyone say for sure which one and if anyone found in it the factory service manual, exactly where did you find it?

The factory service manual specifically states V5 Compressor, 525 viscosity mineral oil on fittings and O rings. (which I think is really R12 oil, but I may just buy some NYLOG Assembly lube).

The reason why I am asking is because I maintain, 5 cars, and an trying to determine if I am going to buy some PAG oil which ones to buy (I'm thinking of buying the plastic bottle type, not the pressurized can type).

So far I can say:
2 cars definitely use PAG46
2 cars use PAG100
The Alero I think uses PAG150

All 5 cars can use the NYLOG Assembly lube or whatever I buy to lubricate the rings. Three of the five have A/C that doesn't work due to leaks and I want to lubricate or replace the O rings, then vacuum and recharge. (although I'll probably vacuum them before and after doing the O rings just to see if that makes any difference).

Note: I'm reasonably sure that my Alero doesn't need any PAG oil, but at least one of the other cars I maintain probably does, so I am likely to buy some PAG46 just for that.

Just to verify, mineral oils were strictly R12 AC systems only and any introduction of these will destroy a PAG oil based A/C system.

Esther oils are compatible with both R12 and 134a systems.

The Alero uses only PAG 150 viscosity oils internally.

Also as a PSA, stay AWAY from those big cans to charge your system that contain dye, stop leak, and the oils.

Stop leaks cause more problems that they fix, the oils that come in those are usually some type of Esther/Pag oil blend that use a "universal viscosity" of both 46 and 100 that will be incompatible with the Alero system, the dyes are fine for finding a leak but shouldn't stay in the system as they'll gum up/harden eventually.

But all oils/dye should only be added using an injector in a closed system. In an open system it's best to replace with new oil after flushing the old out and replacing the TXV and dryer assembly.