A mixed-potential-type sensor was fabricated using yttria-stabilized zirconia and various zinc-based oxide sensing electrodes (SEs) with the goal of detecting hydrocarbons (HCs) in automobile exhausts. Among the various zinc-based oxide SEs examined, ZnCr2O4 was found to give highly selective and sensitive response to C3H6 at 550 degrees C even in the presence of 5 vol % H2O. The Delta emf (electromotive force) of the sensor showed almost linear dependence with the logarithm of C3H6 concentration. In addition, it was found that the sensitivity of the present sensor varied linearly with the carbon number of various HCs examined. (C) 2008 The Electrochemical Society.