I have fitted an electric fan to replace the stock pulley radiator fan. It remains on whenever i turn the key. It doesnt have any thermostat or shut-off system. The cooling for the water is extremely good that even if i drive for more than 100km, i just have to leave the fan for abt 30 seconds & i can dip my finger into the radiator tank. The temp gauge barely touches the bottom line.

Can somebody please tell me how can running below the optimum temperature affect the performance and fuel consumption and perhaps other issues? thanks.