The Mitsubishi ASX is Australia's best-selling small SUV.

Think about that for a moment. Mitsubishi's smallest SUV is getting on for eight years old now, with only a handful of minor updates and style tweaks to keep it fresh along the way, and it's based on a car (the Lancer) so old that Moses might have sat his P-plate test in one.

Explore the 2018 Mitsubishi ASX Range

And yet it's out-performing a host of newer, smarter options with absolute ease. So we spent a week behind the wheel of the top-spec ASX XLS diesel to figure out why.