I have a BMW 740 in Hong Kong, prefer 15W40 or 20W50 in temperature range above -5'C and 5W30 only if temperature is below 0'C. But as I know, almost all BMW in North America prefer 5W30 or ?W30 for all regions, including Florida and California. The climates in Hong Kong and Florida are almost the same,no snow in winter, humid, over 30'C in summer. So why BMW prefer different oil grade in this two regions? Does BMW actually make different kind of engine for different regions?