The data for costs of constructing and running CNG-powered vehicles were obtained for the study. Economic analyses of running the CNG-powered vehicles and that of running diesel vehicles were performed. The initial costs of project and operating costs amounted to N3.71million, N1.31million for CNG, and N3.22million, N2.67million for diesel respectively. This difference in the capital costs is basically due to the addition of the extra parts and connections to convert the diesel-powered vehicle to a bi-fuel-powered vehicle to enable the use of CNG as fuel. The difference in the operating costs revealed that the costs of the two fuels are not the same. The net revenue for CNG is N2.55 million while that for diesel is N1.2 million. This difference in net revenues resulted from the difference in their gross revenues and/or in operating costs. Figures were used to determine the pay-out of the projects which is 1.45 years for CNG and 2.7 years for diesel respectively. The Net Present Value (NPV) and other parameters that make up the project economics were estimated for CNG and diesel. The NPV for CNG at an expected rate of return of 10% is N15.7 million while for diesel, the NPV is N5.86 million. The summary of the result of the calculations of all the parameters examined for both CNG and diesel was also presented. From the whole analysis done it is easily seen that using CNG for powering vehicles is more profitable than using diesel.