Hi All,
Here's my 2 cents:
Oil/water heat exchanger is used in racing for decades with great success. Here's a link to most effective unit to date. Produced by Laminova of Sweden (Part of Opcon corp.)
On our formula cars we tryed every existing solution starting with oil/air than oil/water mocal, setrab and some others. Laminova provided best results.
www.laminova.com
They also have one combined - engine/gearbox oil/water heat exchanger in one unit.
Cheers
Ted