Let’s look at what a medium earth elemental gets.
• Str +10, Dex -2, Con +6, Int -6
• +9 natural armor
• Slam attack for 1d8 damage
• Earth mastery (+1 attack and damage in most situations)
• Push (essentially a lesser version of Improved Bullrush)
• Earth Glide (free movement through earth and stone)
• Darkvision out to 60 feet.
• Immunity to poison, sleep effects, paralysis, and stunning.
• Not subject to critical hits or flanking.
• Unlike most other living creatures, an elemental does not have a dual nature—its soul and body form one unit. When an elemental is slain, no soul is set loose. Spells that restore souls to their bodies, such as raise dead, reincarnate, and resurrection, don’t work on an elemental. It takes a different magical effect, such as limited wish, wish, miracle, or true resurrection, to restore it to life.
• Elementals do not eat, sleep, or breathe.
To state that this template/race should be have ECL +0 is ludicrous, it is a melee characters wet dream set of abilities. Enormous strength and constitution bonus combined with immunity to a broad range of effects, attacks and conditions.
ECL’s have to be reasonably balanced for the most powerful class choice (in this case fighter or Barbarian). If used without monstrous HD I would say at least ECL +4, with the 4 racial HD I would perhaps agree to ECL +3.