In this work, spherically expanding flames are used to measure the unstretched flame propagation speed and Markstein length of an alternative fuel (iso-octane/methane fuel blend) at initial temperatures between 368 and 448 K, and pressures between 1 and 5.5 bar by using the Schlieren photography method. Methane is added in two volumetric fractions of 70% and 95% to iso-octane in a constant volume chamber. Markstein lengths are obtained via nonlinear methodology over an extensive range of equivalence ratios between 0.85 and 1.2. From these new experimental data, a laminar burning velocity correlation based on unburned gas temperature, pressure, equivalence ratio and methane mass fraction was proposed. It is seen that the unstretched flame propagation speed of blended fuel are located between the pure fuels but did not follow simple mole-fraction based weighted average of parent fuels and flame stability is enhanced by adding more methane to the fuel blend. Initial pressure rise has a suppression effect on flame propagation and pure methane receives the most influence from this effect. Initial temperature rise increase the propagating speed in all mixtures. (C) 2015 Elsevier Ltd. All rights reserved.