Originally Posted By: Lubener
Highly unlikely you need to add oil unless you change one of the a/c components.
Unfortunately muppets tend to just add oil and refrigerant indiscriminately because it's easily available in "blow off" cans. The reality is a slow leak loses almost insignificant amounts of oil. The only time you need to add oil is (as you say) you replace a component, or if you've had a catastrophic failure (like a blown hose).
What you *should* do is charge the system up, let it run at idle for about 15 minutes, pull the compressor and drain the oil into a measuring cup. Check that against the manufacturers spec and add the *specified* qty of oil back into the compressor. Very few people do that unfortunately as it's just easier to squirt oil into a system and tell yourself it'll be ok. Sometimes it even is.
Then again, you should charge your system either by weight, or by calculating superheat and subcooling, but nobody does that either.
I don't mind people doing DIY A/C services if it's done right, but it never is. But hey, it blows cold. Just dumps [censored] of refrigerant into the atmosphere, but we can just "top it off" using cheap cans from autozone.
Sorry for the rant.