My question is about 134A systems and when to add more oil - if ever.  Have worked on quite a few air conditioning systems and have gauges etc.. Just like the old R12 days as the vehicle gets older it loses some 134A and system is low.  Put in a can of 134A to top it up and normally ( assuming no large leaks) it is good to go for another year when over the winter it leaks out a little bit and it needs a can next spring.  I know in a perfect system it should not leak out a few ounces over the winter but this is older vehicles (post 1995 so they are 134A built systems) and sure enough a can has to be added in the spring.

  My question is -  how often do people add oil in this situation -  I do not like the leak seal products so I do not add them.  Should I be adding some 134A oil every now and again?

Thanks - Whipper