On my last oil change I switched oil from motorcarft 15-40 to the Mobil one synthetic 5 40. I've noticed that with the synthetic my oil temps run about 5-10 degrees hotter. With conventional they run between 197-199 on the highway unloaded with synthetic there between 203-207 with the same conditions. I always thought synthetic was suppose to run a little cooler. My question is if this is normal or did I get a bad batch of oil or could this be the start to a new problem? Truck has 57000 miles and the current synthetic oil only had about 3000 miles on it.