Abstract: A surface type air to oil cooler enables oil to flow from an inlet and down a first pass of an oil passageway. A first bypass, before the end of the first pass, allows oil to flow from the first pass to a second pass of the oil passageway. A second bypass may exist toward the end of the second pass to allow the oil to flow from the second pass to an outlet before the end of the second pass.

Abstract: A surface type air to oil cooler enables oil to flow from an inlet and down a first pass of an oil passageway. A first bypass, before the end of the first pass, allows oil to flow from the first pass to a second pass of the oil passageway. A second bypass may exist toward the end of the second pass to allow the oil to flow from the second pass to an outlet before the end of the second pass.

Abstract: A heat exchanger comprises: a first medium inlet operable to receive a first medium into the heat exchanger; a first medium outlet operable to expel the first medium from the heat exchanger; a second medium inlet operable to receive a second medium into the heat exchanger; a second medium outlet operable to expel the second medium from the heat exchanger; and a plurality of parallel tubes running from the second medium inlet to the second medium outlet operable to carry the second medium from the second medium inlet to the second medium outlet, the plurality of tubes including: a first section of a first plurality of tubes, at least one of the first plurality of tubes having a first diameter, situated so that the first medium first flows from the first medium inlet over exterior walls of the first plurality of tubes and through gaps between the first plurality of tubes; and a second section of a second plurality of tubes, at least one of the second plurality of tubes having a second diameter that is different