A heat exchange system for use in lubricating systems for aircraft turbofan engine equipment in which a lubricant is provided under pressure to spaces bounded at least in part by surfaces moving relative to one another, the heat exchange system for providing air and lubricant heat exchanges to cool the lubricant at selectively variable rates in the engine fan airstreams. A heat exchanger core (14) is provided in a controlled air flow duct system (11) opening at its plural entrances (12,12') to the engine fan airstreams (13) and having its outlet end opening (16) about at the end of the fan duct nozzle.