Methods and apparatus that change the mobility of formation fluids using thermal and non-thermal stimulation including, an example apparatus to simultaneously provide thermal and non-thermal stimulation to change a mobility of a fluid in a subsurface formation includes one or more containers to hold one or more reactants. Additionally, the example apparatus includes a reactor to initiate a chemical reaction with at least one of the reactants. Further, the example apparatus includes an injector to inject a product of the chemical reaction into a formation. The product of the chemical reaction includes heat and a gaseous diluent to change a mobility of a fluid in a subsurface formation.