Mileage comparisons are totally impossible and quite useless. Even on two vehicles that are equipped exactly alike, because of all the parts that go into said vehicles, mileage can vary greatly. Even the smallest part when looking at manufacturer variations play a part in the outcome. And depending on the machining and boring, whether they are new dies or worn, whether the guy doing the machining or assembly is having a good or bad day or in final assembly how it is bolted, screwed, or fitted together, makes a difference. And that is just the engine. Then you throw in the electronics that control and the driver, environmental differences, and any other number of factors, it's no wonder that individual numbers vary so much.
Just try to get the best that your truck can get if it is of concern, and it is what it is. Or, just enjoy the ride.