+1 Both compressors have roughly the same internal volume for moving freon, but the Lexus has a variable displacement compressor where the old school Brat compressor is a fixed displacement compressor so it's pumping full tilt all the time (unless the pressure switch shuts it off). The variable displacement may be mechanical or ECU controlled and is based off system pressures, flow and temp to yield acceptable cooling with minimal load on the engine to keep your MPGs up. Add to that, as you stated, the cabin size difference (Lexus being 2-3x the volume of a Brat) and the fact that R134 does not coll as well as R12 and there you have it. Your Lexus may also be having issues. Low charge, sticky temp door, plugged or stuck orifice/TXV or a cooling fan or condensor air flow issue. Give me old school AC any day.