¹²C/¹³C vs. [Fe/H] for core He-burning and RGB stars in our sample (squares and circles, respectively) compared with the BGM simulations for core He-burning stars only (dots) of the Kepler field and taking into account or not the effects of thermohaline mixing (right and left panels, respectively). The stellar mass is colour-coded for both observations (using seismic determinations from PARAM) and simulations (predicted by BGM using STAREVOL stellar evolution models from Lagarde et al. 2017, 2019). In the right panel the mass loss rate is decreased on the RGB by a factor of two compared to the left and middle panels (see text for details).