For MRI with a multi-receiver RF coil, one image per coil element and per time frame is obtained. The final image is typically calculated from the root sum of squares (rSoS) combination across channels. While this combination approach is quasi-optimal for SNR, it is not necessarily optimal for temporal SNR (tSNR) of the time-series. We present two analytical and voxel-wise coil combination expressions reaching optimality in tSNR and t-score for the mean (TSM) respectively. Their BOLD sensitivity is compared to the gold standard covariance root sum of squares. Both improved tSNR and TSM but yielded weaker t-scores than covSoS.