Upper panel: variability of R Car based on the visual magnitude from AAVSO data and the angular diameters determined with VLTI-GRAVITY (binned in 2-week intervals). For clarity, we merged CO bands θ_CO(2-0) with θ_CO(3-1) and θ_CO(4-2) with θ_CO(5-3). Different colors correspond to the continuum and to regions of the extended atmosphere. Lower panel: phase diagram of brightness and diameter variability. Solid lines represent the sine fits for P = 307.4 d (same colors as atmospheric layers). Phases φ_vis for which the fits to angular diameters reach maximum are denoted in the caption.