Aside from normal usage: Matlab, programming suites, as a mechanical engineer you'll also use CFD and CAD programs which are pretty computer heavy. It might not be necessary to do these on your laptop though, although it will always be convenient and potentially quicker depending on how good your uni's computers are.
So to be on the safe side I'd say get a small, cheap laptop with an i7 and 8GB of memory, graphics won't matter too much unless you want to game, same goes for having an SSD.