On Wed, 27 May 2009 21:43:16 +0200, Daniele Fua
wrote:

Vinegar might work as well with far less danger for you and the
environment but slower.
Classic Coca-Cola also... it used to contain small quantities of
sulphuric acid and old-times mechanics would use it for frozen
engines.
Never sulphuric. Phosphoric acid is a common ingredient in soft
drinks.

Casady