Pros: Inexpensive (in the larger quantities) effective, no harsh chemicals.
I have used many fuel treatments over the years. Honestly, I never could tell if the worked or not. A friend recommended Lucas. I looked at it. a 5.25 oz bottle of what looked like nothing more than motor oil. This tiny bottle was supposed to treat 25 gallons. Of course I hesitated.
Then, comes winter and a bit of rough running. I saw the Lucas bottle again and said what the heck! I gave it a shot.
It seems to work immediately! Wow! Then engine ran a lot smoother and had better response in accelleration.
Additionally, I really noticed fuel savings. Very impressive. This product actually works! It is a first.
This product is what is called an "Upper Cyliner Lubricant" It is designed to lubricate and clean injectors, carbs, piston rings, and valve seats. Fuel pumps will also get some benefit.
The product has no harsh chemicals or solvents that could harm easily corroded components or rubber hoses.
It is simply a very concentrated, very "slick" oil with high dteregent abilities. 5 ounces will treat 25 gallons.
It costs about $6 for a 5 oz bottle. HOWEVER, you can get it in a quart bottle for $9 and a Gallon jug for $20 at auto parts stores. Your savings increase in quantity.
To get a benefit from this product, you need to use it all the time. Obviously, since if you do not use it, you do not get the benefit of the lubrication.
Once, I tried the tried and True Marvel Mystery Oil, which I use as a helper for my engine oil. It is also an upper cylinder lube for fuel. I noticed no benefit in my van.
All in all a great product. I recommend the quart size, as you get more for less money, and your fuel savings vs cost of product will pay for it.
I use it all the time and save possibly 20% in gas mileage, and have a cleaner, smoother engine.