I have a 1996 Dodge Neon so it's getting up there in years. I want to keep my engine clean and running for as long as I can before I have to go purchase a new car (I just got this one payed off). One way I try to keep my engine running smoothly and also save on a little gas is by using STP Gas Treatment. It's very easy to put in the car. Just pour a bottle in the gas tank after a fill up. You can buy individual bottles but I tend to buy the 3 pack for around $2.50 a pack. I buy the 8 FL OZ bottles since I have a smaller car. You can also purchase a larger bottle for larger vehicles.
This product is designed to remove carbon accumulation, gum and varnish deposits from the fuel system. This product also removes water from the fuel line and the fuel. It also saves gas by keeping the fuel intake system clean.
This product does not work immediately after you poor it into your gas tank. It does take it a while to get through your fuel line system but once it does I can tell a difference in the feel of the engine in my car.
There a lot of warnings on the this product mainly of not swallowing product because it would be harmful or fatal and obviously to keep it out of reach from children.