The present study extends the full numerical EHL solution to wide parameter ranges that cover practical and severe operating conditions commonly found in heavy-duty components. This article is the fourth part of the present study, and is focused on the effect of material properties on the film thickness, following three previous papers that investigated the effects of speed, load, and contact geometry, respectively. In this article, the pressure-viscosity coefficient is varied in a range from zero to 72.8 GPa−1 and the elastic modulus from 80 to 400 GPa, sufficiently wide to cover different materials and lubricants commonly used in industries. More than 500 cases have been analyzed, and results show that in the extended parameter ranges the relationships between the material properties and the film thickness still primarily follow the simple power rules proposed by the conventional EHL theory. However, the exponents in the power-law functions no longer appear to be constants. They are indeed functions of speed and load. For the relationship between the pressure-viscosity coefficient and the central film thickness, the exponent appears to be quite close to 0.53 proposed by the Hamrock-Dowson formula if the speed and the load are moderate. When the speed is low and/or the load is heavy, this exponent may be considerably greater. The same trend is observed for the relationship between the elastic modulus and the film thickness. At moderate loads and speeds, the exponent is close to −0.073, which is used in the Hamrock and Dowson formula. When the speed is decreased and/or the load increased, the exponent may become positive. It is found, in addition, that the exponents in these relationships are only weakly affected by contact ellipticity.