Review on Liqui Moly 2001 Valve Clean by Jarrett Young

so this works pretty well through the gas tank for cars with injectors that inject into the valves and not straight into the combustion chamber. If your car has direct injection (the latest) there is a YouTube video on how to gently spray a valve cleaner directly into the throttle body and get great results with before and after photos of the intake valves. Direct injection cars are notorious for dirt build-up, so keep an eye out. On all gas powered vehicles, clean the valve in the gas tank and make sure there is at least 7 gallons before refueling. The canister is labeled for 20 gallons, but a stronger one can to 7 gallon ratio may be more effective. Worth a try if your car is a bit rough at idle or you notice a drop in fuel economy/efficiency over a period of time.