The removal of fuel subsidies in Nigeria in May 2023 created an unprecedented economic imperative for Compressed Natural Gas (CNG) adoption, yet empirical evidence on CNG vehicle performance compared to Premium Motor Spirit (PMS) vehicles among early adopters remains limited. This study compares the operational, economic, and environmental performance of CNG against PMS vehicles among 25 early adopters in Abuja's Federal Capital Territory. Employing a convergent parallel mixed-methods design, data were collected through semi-structured interviews, vehicle log extraction, and field observation, complemented by 25 key informant interviews and 4 focus group discussions. Paired t-tests and effect size calculations (Cohen's d) were employed for comparative analysis. CNG delivers 30.5% better fuel efficiency (8.8 km/liter PMS vs. 11.5 km/kg CNG, d=4.80), though with a 29.1% reduction in vehicle range (441 km to 312 km per tank, d=4.85). Maintenance benefits are substantial with 41.3% lower monthly costs (N31,500 to N18,500), 52.2% fewer engine repairs, and 48.0% fewer unscheduled breakdowns (all p<0.001). Economically, fuel cost per kilometer decreased by 54.7% (N13.2 to N6.0), weekly fuel expenditure dropped by N21,700 (55.0%), and daily profit after fuel increased by 59.7% (N5,260 to N8,360), with a mean payback period of just 7.9 months representing a 161% annual return on investment. Environmental improvements are dramatic with 96% reporting less visible smoke, 92% reporting quieter operation, and 92% reporting better cabin air quality. Despite operational challenges including limited stations (92% reporting) and queuing time (84%), 92% of early adopters would recommend CNG to other drivers. The study concludes that CNG delivers superior operational, economic, and environmental performance that overwhelmingly outweighs moderate performance trade-offs, providing compelling evidence for accelerating CNG adoption in Abuja's public transport sector.