<p>The impact of toxic emissions on ecosystems and environmental degradation remains a critical global challenge, largely driven by incomplete hydrocarbon combustion from human activities. This study examines the temperature distribution of a couple stress fluid with viscous heating flowing through a channel to better understand and enhance combustion efficiency. A two-step exothermic reaction–diffusion mechanism is incorporated into the viscoelastic fluid model to facilitate more complete combustion. The analysis assumes negligible reactant consumption, with fluid motion driven by pressure forces and influenced by an induced Lorentz force and a pre-exponential factor. The governing partial differential equations are formulated with fixed-wall and Navier slip boundary conditions and transformed into a dimensionless invariant system. The resulting equations are solved using the Galerkin weighted residual method to capture the coupled effects of viscous heating, material nonlinearity, and chemical reactivity. Results, presented in both tabular and graphical forms, show that the inclusion of a second-step exothermic reaction significantly increases heat distribution, thereby enhancing combustion completeness. Moreover, fluid viscosity increases with higher material dilatant effects, contributing to more stable flow behavior. These findings suggest that while heat-generating mechanisms can promote combustion, they must be carefully managed to avoid excessive temperature rise that may lead to thermal runaway or system thermal blow-up. The study provides theoretical insights that can inform the design of more efficient, environmentally sustainable combustion and lubrication systems.</p>