Heating Issue In Nissan Sunny

Best answer is you kindly check the engine oil you are using for your car is suitable for your engine in your region. As engine oil characteristic in viscosity varies with temperature and altitude you are using it. I am hoping the you are riding your car in Indian roads. With popularity of this car on plains is higher than the mountains sepically in southern Indian markets. The recommended engine oil should be at least 10w -40 in summer/ winter or 15w -40 if your car is driving on regions where temperature goes 45+ easily or close to it for most of the year. Still I would say one more thing please refer your user manual which you get with the car. And ask your car company. to help you with the selecting the grade of engine oil as per the terrain your are driving your car. please do consider one thing 5w-30/ 5w-40 are meant for extreme cold weather areas and are not good in high temperate regions. Most of the mechanics will encourage you to buy 5w-xx stock because of less knowledge or to make profit out of it. But, its your engine which takes the load of the not appropriate engine oil you give to the car.I do hope this will help you cool down your car issues.