When the weather is hot the car runs sluggish temp. Gage is fine

This really is a situation where a technician would need to have the vehicle and diagnose it. The description is to vague to really give any direction. We apologize.

The vehicle is rated for 5w-30 or 10-w30. If you are living in a warm area you might need the 5w-30, but have the 10w-30.