ABSOLUTELY NOT, IF the oil temperature is not REGULARLY exceeding 115-120°C!

You want the temperature to hit around 110°C on track, as this will burn off any excess water that you get in the engine from the heating / cooling proces, so if it is around this in hard use, then spot on . The standard Cossie set-up is pretty good and takes some serious abuse / power to exceed these temps.

You would be better off fitting a big wing sump for extra capacity, as the 3.75 litres of a standard 4x4 sump is pretty marginal . This will improve cooling due to the increased capacity, as well as the additional benefit of having a sufficient amount of oil for an engine at this level of power (plus helping with any surge issues).

So to answer your question, first I would measure your oil temps and then if you were concerned, then I would fit a big wing sump - the oil cooler would be a last resort. I am now only having to fit one on my car, as it is only with the new engine that temps have gone over 120°C on track.....

FYI a good oil such as the Silkolene ProS 10w50 does not break down until 130°C.....