I am workimg on mcquay splt systems that have had alot of service issues(long story). My question is the tandems have a oil crossover between compressors. Should the compressors have the same oil level. We have units that the one compressor is normal to high and the other compressor you can barely see any oil. Whatr is the real purpose of the oil crossover tube. These units have had return issues and have exvs. I am just looking for some general input.