Isuzu Forums - Isuzu Enthusiasts Forum - troop5er 1995 swb oil leak

Hi have just bought trooper swb 1995 3.1 d and woke up to find a cookie size oil patch under the engine ...does idle very badly when cold but when run to temp is fine....no smoke out of rear or bad running ,,,,,,,is this to be concerned with or just keep topped up when needed,,,,,,,,,,,,,,,says on mot advisory that it has diff leak aswell but that is not noticable to me.........only done 115k and runs fine will it be a problem or not.