You won't sea a oil leak on a car not enough oil in a system only place you can sea a leaksometimes is on a on condensor when it's been gases multiple times we pressure test at ten bar for minimum one hr if gauges drop at all you have a leak the vacumn test don't work on cars I've had leaks on cars then used a torr gauge and it's held a vacumn perfect on that model the condensor will be leaking or the pipes that go to condensor on O rings they bubble after twenty mins
When you have traced leak and regas if o ring add 5 cc of oil if you fit condensor 20 cc of oil also watch the condensor fans as prone to failure on plug to fan we very rarely uv dye there is no need just patience ta charlie just as reference I would never send a vechicle out with a vacumn on ac circuit