QED calculations of energy levels of heliumlike ions with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>5</mml:mn><mml:mo>≤</mml:mo><mml:mi>Z</mml:mi><mml:mo>≤</mml:mo><mml:mn>30</mml:mn></mml:mrow></mml:math>

A calculation of two-electron QED effects to all orders in the nuclear binding strength parameter $Z\alpha$ is presented for ground and $n = 2$ excited states helium-like ions. After subtracting first terms expansion from all-order results, we identify higher-order order $m\alpha^7$ higher. Combining remainder with results complete through $m\alpha^6$ [V. A. Yerokhin K. Pachucki, Phys. Rev. 81, 022507 (2010)], obtain most accurate theoretical predictions non-mixing $n=2$ ions $Z 5-30$. For mixing $2^1 P_1$ $2^3 states, extend previous by evaluating correction show that it defines uncertainty calculations $LS$ coupling > 10$.