If you haven’t used any sort of fuel additive in tens (or hundreds) of thousands of miles and wanted a pour-in product, we would suggest using our B-12 Chemtool Total Fuel System Clean-Up (part #2616). This product will help remove any free water as well as clean any gum, varnish or other fuel related deposits from your fuel pump, fuel lines, intake valves, and fuel injectors. If you still have a bit of a rough idle or some cold-weather hesitation, you may need some additional cleaning. In that case, we would recommend using our Professional 3-Step Fuel System Maintenance Kit (part #2630). It contains an air intake and throttle body cleaner, a combustion chamber cleaner (applied via manifold vacuum through either the PCV valve or the brake booster), and a can of our B-12 Chemtool Fuel Treatment. The kit may sound a little intimidating, but it’s pretty simple to use and even comes with an instructional DVD.