I recently purchased a used impala and use the vehicle for looong commutes back and forth to school and work. my question, is it ok/safe to use mobil 1 full synthetic 15W-50 in the summer(it is currently 106 degrees outside) i am not worried about gas mileage or engine power lose i just want to protect the engine as best i can especially in this rediculous heat, my buddy is a mechanical engineer and tells me never to use it because it will eventually ruin my oil pump. ive been using this oil only during the summer with no problems, im no mechanic so thoughts and suggestions on this are very appreciated. its a 2007 impala 3.5 litre flex fuel engine

 

Do not run that oil it will hurt your car worse. It was not designed for it. The manufactures pay engineers lots of money to design engines. Use only the correct weight oil 5w-30. Using thicker oil may give you a higher oil pressure but it reduces the volume of oil circulating through the engine. Less oil volume will be worse the increased pressure. Think of it like a garden hose, when you put your thumb over the end the pressure goes up but there is less water coming out. The first # in oil weight represents how thick the oil is at cold start (outside temp). Increasing to a 15w means the oil takes longer to get to the top of engine.