Nissan Qashqai Engine Problems
Nissan Qashqai 2014: Coolant problems
It’s a pretty standard offer, and while I agree that the heater core should last longer your car is five years old, it’s out of the factory warranty period. I would take the offer and move on.
Nissan Qashqai 2015: Should I buy a petrol or diesel?
There is nothing to suggest the diesel is a problem, and I would question your mechanic’s advice. The high fuel pressure of today’s diesels can result in worn injectors and they can cost upwards of $2000 to replace. Other than that there’s nothing to be overly concerned about.
Should I buy a petrol or diesel car?
Diesels work at their best when they're running fully warmed-up and for long periods. If you aren't doing a reasonable amount of kilometres you can have trouble with the DPF system in the car, which can become clogged and require servicing to clear it. In your situation, doing very short trips to and from work each day I would buy the petrol variant.