I tow with an '06 V10. I have towed almost 16k miles in the last three summers. From Texas out to california up to yellowstone to south dakota and back and forth across Colorado. Million Dollar HWY(550), Monarch pass, I70. My tariler is about 9500lbs. I haven't been anywhere yet I can't go the speed limit, sometimes passing other RV/trailers. Think about all the gas engines mentioned in this thread all have twice the HP and the same TQ as the old Ford 7.3 that everyone loved to tow with. Just my .02 cents