Considerable uncertainty exists over the potential benefit of zirconia thermal barrier coatings (TBCs) in diesel engines, as well as their possible effect on NO x and other emissions. In the present study, a simple furnace system was used to identify catalytic combustion effects in the ignition and combustion of propane/air mixtures over catalyst-doped m-ZrO 2 spheres. Three classes of catalysts were examined: zirconia-stabilizing oxides (CeO 2 , Y 2 O 3 , MgO), transition metal oxides (Co 3 O 4 , Cr 2 O 3 , Fe 2 O 3 ), and noble metals (Pt). Each class exhibited characteristic combustion effects, with the ignition temperature increasing, e.g., from approximately 200°C for Pt to 550°C for the stabilizing oxides. The results are discussed in relation to diesel engine combustion, including the controversial Woschni effect wherein heat-insulating TBCs are postulated to actually increase heat loss from the combustion chamber.