Observed L_SiO (same as the red open circles in Fig. 6) and F_CO, in blue and red circles, respectively, with respect to the envelope masses (M_env) for individual sources. The second red point from the left corresponds to CygX-N40 MM1, for which we have an F_CO measurement, but no L_SiO. The dashed red line shows the linear correlation of F_CO = 7.5 × 10^-5M_env, originally found by Bontemps et al. (1996) for low-mass protostars, and confirmed in Duarte-Cabral et al. (2013) to extend to the high-mass regime. The dashed blue line shows the linear correlation of L_SiO ≃ 5 × 10⁶M_env that we find for the blue points. This figure accentuates the fact that L_SiO of individual outflows follows the same trend as F_CO (both being ∝M_env), even though it introduces more scatter with respect to the linear relation found for F_CO.