Well, I have seen the ads and all, but I never purchased the products until about 3 weeks ago. They are kinda pricey ($10) for a bottle that goes in the crankcase, and ($5) for a complete fuel system cleaner. Since I didn't know how they acted, I didn't put them in my truck--I put them in my commuter car--a '93 Honda Accord EX coupe. It has 155,000k on the clock and it and has yielded roughly 25-26 extremely reliable mpg (city-hwy mixed) for the past few years.
Like I said, put the stuff in and WOW! The engine smoothed out and it ran even better. With the additive in the crankcase and in the fuel system, I got 32 mpg on the first tank--not bad for a 15 year-old car with 150k+ miles. That's a 6-7 mpg improvement. And I don't drive it like a woman--I have to get into it to get it to move how I want it to---usually 3500 to 4000 RPMs per shift.
Like other fuel additives, I thought it would only get 32 mpg for that tank. But after the fuel additive was gone and with a fresh tank of 87 octane, it got the same mpg on the 2nd tank without the fuel additive. I have run 3 new tanks of gas and have received a constant 31-32 mpg. It is freakin magic.
Guys--I would HIGHLY recommend that you put this stuff in your trucks and cars. I am going to put it in my truck the next time I drive it. I can't even explain to you how well this stuff works. Doooooo it!!!