Never tried any of the over the counter stuff. But have used a product from POR15 (http://www.por15.com) in my MG tanks, which are 30+ years, old with great sucess. They have dealers all over the place, there could be a local one near you, if not shipping is same or next day.

They also make great rust products.


08' Jeep Wrangler
64' Plymouth Sport Fury 383
58' Triumph TR-3A