NOTHING is free. You're paying for those oil changes in the purchase price of the truck, so I sure as heck wouldn't let them go to waste. Throwing those oil changes away and then spending even more money on a full synthetic oil would be a huge waste. There's absolutely nothing wrong with the dexos blend, and running a full synthetic instead isn't going to magically extend the life of your engine if you're changing it when the OLM tells you to.