What to clean gas tank with?

I've done a few tanks in my time, all with the same method....

Go to the hardware store and get yourself a one gallon jug of Muriatic acid, or pool cleaner as it may be called. Dump the old gas out and spray the inside out with a garden hose. Then dump in the muriatic acid in and cork up the filler neck and sending unit holes. Swish the muriatic around for a few minutes and let it sit, then do it again, and again until your're satisfied that the tank should be clean inside. Then open the cork and dump out the acid into a pail and return it to the jug. Spray out the tank with the hose again and dry it either with the wife's hairdryer or compressed air.

The acid will neutralize any flash rust in the tank, loosen any heavier scaly rust and will also etch the inside of the tank and allow it to completely dry and not rust again. Muriatic isn't dangerous if handled with a little care, and is water soluable so it works well for this application!! Thats how I do it!! Geof