My knee-jerk reaction here is to call all fuel and oil additives snake oil, meaning they really aren’t worth it. I think fuel and oil additives are a case of perceived value. You go to the auto parts store, pick up a bottle of “make your engine happy,” dump it in, and you suddenly start getting more power and better MPG out of your vehicle. This is why I say “perceived.” I’m sure there are people out there who swear by product X. I’m not saying product X isn’t a good product. I’m saying that product X is different things to different people. It’s money in the pockets of the people selling product X more than anything else. Am I opposed to this? No, I’m a capitalist. But as a capitalist I like to save money. For me, I’d rather save my money than put “make your engine happy” in my tank or crankcase. I prefer old-fashioned service and maintenance to keep my engine efficient. Dumping stuff in my tank just seems like a shortcut that will get me lost rather than to my destination. You, however, can do what you like. One thing I will say is that when used properly, fuel and oil additives don’t do any harm. So if they make you feel good, use them. If you want to save money, don’t spend it on fuel and oil additives.