Also known as 7.5L. In a 10-year old F250. Has 50K miles. Used maybe 5K mis/year and most of it towing almost 10,000lbs. Not a daily driver. Thus far I have been using good dino 10w-30. Wonder if Mobil 1 synthetic would benefit it, also 10w-30. Or is there an even better synthetic? Royal Purple maybe? If there is any benefit, then the cost is negligible in light of what professional engine service costs, what new vehicles cost (especially of that heavy-duty caliber) etc. I have been trying to use the best components, best flter, best fluids, and more. I want to keep it as long as possible given low miles and have been doing a lot of preemptive work. Anybody else with 460 in a heavy-duty truck?