Is fuel system cleaning suggested? If so, what mileage?

Yes, keeping the fuel system clean is important. Fuel cleaner does several important things. It keeps the "fuel level sensor" in your gas tank from sticking and giving you a false level reading on your dash "fuel level gauge" If your car has either fuel injectors or a carborator, it will keep clean the very small valves in either. Gasoline breaks down quickly. After 3 or 4 weeks it gets rather like maple syrup. Starts to block fuel flow. Gas cleaner additive also cleans your engines valves and keeps damaging carbon from forming on them. For maintenice, use 1 bottle of "Gumout carb and fuel injector cleaner" every 6 months. About $2.00 at your local auto parts store. Add 1 bottle to 1/2 tank of gas. Don't refil gas tank untill almost empty so that you don't dilute it too much. Your car may run a little ruff during that time. If your car is running really poorly, and your mechanic says it's time to clean your system. He will need to pressure clean your gas system. But, before you do.. The STRONGEST gas system cleaner is "STP" fuel Cleaner. A bottle runs about $5 at your car parts store. Use per directions. It is strong enough to unblock stubborn (dirty) fuel injectors. Try it your self first and save money.. The J...