I wonder if anyone actually runs an oil cooler thermostat - I don't know that I've heard of it... I don't run an oil cooler at all on my MK2 S
However, I have an oil cooler thermostat on my Polo GTI that is a sandwich plate between the oil filter and filter head. It has an inbuilt bypass thermostat that is open until the oil hits 92°. The stock Polo oil filter doesn't fit anymore as it is quite tall. I am now using the same oil filter on the Polo that I do on the mini - a Z418 - they are the same diameter and have the same thread - I forget the diameter but the thread is 3/4"/16 TPI
This means that it'd be perfectly feasible to use the same oil filter thermostat on the mini - same size, same thread - it'd suit what you want to do quite well and was pretty cheap.
I got them from
http://www.mattlewisracing.co.ukhere are the parts I ordered
1 x MLR.TO, Mocal 605 3/4UNF Oil Cooler Sandwich Plate Centre Bolt
1 x MLR.BND, Mocal OTSP1X-92 92° Oil Cooler Thermostat Take Off Sandwich Plate
I also ordered a pair of "AN" fitting adapters, I wouldn't do that again, I'd use barb fittings
1 x MLR.AAU, Mocal MMS0-8-10 1/2BSP - -10JIC Male/Male Adaptor Sandwich Plate Fittings (Pair)
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