My 2010 SIDI SV6 has been maintained over and above what the service book requires. Im up to 165***km now. Does anyone have an recommendations, should I go from a 5W - 30 to a 5W - 40 to make it just that bit thicker? We bought the car new in Darwin so its always been in the heat, humidity and high air temps. Now we live in the Adelaide Hills where the temps are so much lower besides a couple of weeks of heat wave. Does that mean I should use a different oil? Oh and does anyone recommend the use of STP oil treatment? Suppose to protect on start up.