Hello everyone. I just recently picked up a 2000 Ford super duty 7.3 power stroke truck. It has 252k on the odometer. I bought the truck from a wholesaler, so he had no idea of what type of oil the previous owner was using. I've been driving the truck on and off for the past couple of months and it runs great. I changed the oil and the very next day, it started running rough. I used Mobile Delvac 15-40 and a Wix filter. I've had several of these trucks and know that they can be picky on oil,but have never had one act like this. I was just wondering if it is possible that the previous owner had been running a synthetic or a blend, and me swapping back to a 15-40 dino oil could be messing with the injector pressure somehow? Thanks