The E Tank is an item that originally appeared in the Mega Man Classic series, from Mega Man 2 to Mega Man 7. It is a round can, usually the same color as Mega Man's suit. When used, it completely refils Mega Man's health bar. It couldn't be acquired from enemies like health energy or weapon energy capsules. They usually appear once or twice in any given levels. A maximum of 9 E Tanks can be held in games 3-6 and 4 in 2 and 7.
 Other Tanks
Related ThreadsX1-3 Sub-Tank setup or X4-6? - last post by @ Feb 12, 2002
E-tanks in hard mode?? - last post by @ Apr 4, 2008
sub tanks and thier location - last post by @ Nov 30, 2011
Heart Tank: Locations - last post @ Apr 21, 2009
Megaman 9 E-Tank energy drinks?? - last post @ Apr 13, 2010