I'm going to view a 2015 Zafira Tourer this morning but I've looked at the latest MOT and saw an advisory saying "Oil leak, but not excessive". How concerned should I be? Would it be best to avoid it?
Oil leak can mean anything from a minor problem such as a rocker gasket or sump washer to a cracked casing or serious gasket failure. If its a car you want then you (or a mechanic) needs to have a really good look to see what the problem is and negotiate accordingly.
The trouble is with crowded modern engine bays its not always easy for an amateur to be sure whats amiss.