If you are fitting a new oil cooler or even simply replacing your old one, new hose are sure something to consider. The hose length is such that it is assumed you are locating the cooler in the original location as found on the cooper "S".
The correct running temperature of the oil is perhaps even more important than the water/coolant temperatures - so let us consider how to control them. Mainly because it seems to be the most misunderstood of the whole process, and oil cooler fitment almost a reflex when over-heating occurs where a tuned engine of any type is concerned. And in many cases on standard production road cars for that matter.