Problems with the cam phasers for sure. I was concerned runing the 15- 40w, but havent had a problem. I had to do something! As i couldn't kep losing engines due to heat. 125 to 130 degres going over town's pass heavy with no sense and your foot in it will do it. Fleet vehicles get used hard,, they don't care until they are way off road out in the desert in 125 degrees with no cell service, then its my fault.