We get temp'* up to 114* in the summer and i use 5w/30 Mobile 1 year round. We have put 165,000 miles on our car and the 5w/30 works just fine. And my wife drives the car pretty hard. We also drive this car in the mountains(up to 10,000 feet) on some pretty steep grades(up to 29%), the engine just keeps going and going, it wont even burn 1 qt. of oil in 10,000 miles.