I have a 2018 F-150 with a 5.0L engine with GDI and PFI fuel delivery. I currently have Mobil 5w20 extended mileage synthetic in it. It has 29,000 miles. This oil has 3,500 miles on it and is a quart low. I previously had Valvoline 5w20 synthetic in it with same problem but don't remember the mileage at which I added oil. I do not run this pickup hard. It's mostly a grocery hauler. The temperature gauge runs normal. With the reading I have done, I'm leaning towards an oil volatility problem. Would a PAO Group IV oil solve the problem. I have a problem finding oil volatility readings on different brands of oil in the Group III oils. Also with this engine having partial GDI fuel delivery along with PFI, is there a problem with carbon buildup on valves.