CB,
It may be worth your , and the clubs while , changing to a thinner grade of oil during the winter season, even if ground temps remain somewhat lower than normal.
I also concur with the others that a gauge temp check should be carried out, and maybe a small blanking plate over part of the oil cooler may help to keep temps. up. If the oil pressure is normal
then it is probably ok, but I`d get an engineer to check it out.