Transmission gear shift control techniques can include calculating, at a controller of a vehicle powered by an internal combustion engine, the controller including one or more processors, brake specific fuel consumption (BSFC) for each of: (i) a current gear of a transmission of the vehicle, (ii) a lower gear than the current gear of the transmission, and (iii) a higher gear than the current gear of the transmission, wherein the transmission is one of a manual transmission and an automatic transmission operating in a manual mode. The techniques can include determining, at the controller, which of the current gear, the lower gear, and the higher gear has a smallest BSFC to obtain a desired gear of the transmission. The techniques can also include outputting, from the controller, an indication to shift the transmission to the desired gear.