The cap-less fuel filler system. I had some gas in a 5 gallon container and tried to pour into that tiny, ridiculous emergency funnel that Ford includes with the truck. Impossible. Plus none of my funnels (4 of them) fit in Ford's crazy filler neck. I think that in all of my years that I might have lost one cap. This is a case of over engineering something that didn't need it (I'm an engineer, by the way, and my wife has accused me of that occasionally). I might not have explained that very well, so take out that funnel, before you need it, and stick it in the filler tube. If you ever have to get a can of gas, make sure it comes with a spout and not just the open can to pour with.