Both the petrol and diesel versions of the 2018 ASX used a timing chain rather than a toother rubber timing belt. That means both engines’ timing chains should be good for the life of the engine, although in practice that hasn’t always been the case and some engines do, in fact, need new timing chains if wear develops in the chain or its tensioners. Neither Mitsubishi engine has thus far demonstrated that trait, however, and it’s far less common if the engine has been serviced correctly. The task of the timing chain or timing belt is exactly the same: They take drive from the engine’s crankshaft to the camshaft and, in the process, keep all the moving parts in harmony. Many car makers moved away from a timing chain to the rubber, toothed drive belt as a way of simplifying engine design and driving down the cost of each engine. The rubber timing belt is also quieter in its operation and is also less prone to stretching (as a timing chain can) so the camshaft stays in perfect synch with the rest of the engine’s rotating parts. It’s a simpler design because it doesn’t need to be tensioned via oil pressure from the engine as many timing chain systems are. The timing chain, meanwhile, is preferred by some manufacturers because it should last the lifetime of the engine and never need replacement. This isn’t always the case, however, and some engine designs from a variety of manufacturers suffer problems in this regard. But, in a properly maintained engine of sound design, the timing chain should never need attention, while the rubber timing belt generally requires periodic replacement, typically between 60,000 and 120,000km depending on the manufacturer.