The effect of rolling resistance R on fuel consumption of radial passenger and truck tires is discussed in this paper. The model equation for the rolling loss R was directly proportional to tire load W (R α W) and inversely proportional to inflation pressure p (R α 1/px). These relationships were experimentally quantified. Using manufacturer’s recommended values for load W and pressure p as reference points the R values for different overload conditions (from +10 to +100%) at constant p were estimated. Similarly, the required p values to support 10 to 50% additional load to maintain original R were also estimated. Then the estimated R values for different overload/inflation pressure conditions were combined with the fuel saving factor F (obtained from published literature results). Then the relative change in fuel consumption of truck/bus tires for different load/pressure combinations vis-a-vis the fuel use for the manufacturer’s recommended W and p values was evaluated. The present analysis showed that for the same amount of fuel use a truck carrying a 100% overload and making one round trip would correspond to slightly more than two round trips by a truck of same size carrying the recommended load. Finally, a possible method of optimizing fuel use by adjusting the tire load/pressure conditions was suggested. All these estimates were obtained for radial tires. The author feels that the same methodology is applicable for bias tires also.