An automotive heat exchanger (1) typically for use as a gas cooler in an automotive HVAC system having refrigerant operating in transcritical or supercritical state has an inlet header (6) and an outlet header (7) and at least two rows of tube lengths (2,3). A first row of tube lengths (2) carry working fluid in a first direction away from the inlet header (6) and a second row of tube lengths (3) carry working fluid in a direction opposed to the first direction toward the outlet header (7). The headers (6,7) are arranged in close proximity on the same side of the heat exchanger (1), an air gap separation or thermal insulator separation being provided between the headers (6,7).