Are the 2 types indeed incompatible? The reason I ask is that motor oils surely come in "blends" which are neither all-dino or all-synthetic. I don't see why A/C oil would be any different. Maybe I'm wrong...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280