Western featuring a Criollo horse

I watched a western many years ago which featured a young guy being chased through mountainous country either by bandits or a posse, but he has a special breed of horse an Argentinian Criollo, famed for their strength and stamina. I have never forgotten the criollo horse, but I don't know anything else about the movie, except there was an old man
sort of chill wills, gabby hayes type, and a teenage boy the boy rides off on the criollo leading the posse away through the most difficult country where their mounts where no match for the criollo. I would love to find out the title and watch it again.