We address a controversial issue of liquid-gas asymmetry in fluids that has been a subject of prolonged discussions for more than a century since Cailletet and Mathias' discovery of the empirical "law' of rectilinear diameter. By combining accurate liquid-vapor coexistence and heat-capacity data, we have unambiguously separated two non-analytical contributions of liquid-gas asymmetry in fluid criticality and proved the validity of "complete scaling" [Fisher et al., Phys. Rev. Lett. 85, 696 (2000)]. We have also developed a method to obtain two scaling-field coefficients, responsible for the two sources of the asymmetry, from mean-field equations of state. Since the asymmetry effects are completely determined by Ising critical exponents, there is no need for a special renormalization-group theoretical treatment of asymmetric fluid criticality.