Temperature gradient averaged over time of the G2V (left column), K0V (middle), and M2V (right) stars. Top row: mean temperature gradient ∇ = ∂ ln〈T〉_τ/∂ ln〈p〉_τ computed from the mean stratification of temperature and pressure of the simulations run using the 18OB (black curve), 4OB (blue), and grey (red) opacity setups. Bottom row: relative difference of ∇ computed with 4OB (blue curve) and grey (red) compared to ∇ obtained using 18OB.