With 15w50, the 15 number is for when the oil is at ambient temp not when it is hot after running. The 50 weight the thickness or viscosity number after it is warmed up. Use Amsoil 5w30 and you will be better off. When you first start your car is when the most wear occurs. Bob is the Oil guy wrote a good bit of information regarding what oil to use. I doubt you will use 15w50 after you read this. Good Luck
http://www.bobistheoilguy.com/motor-oil-101/