I think the general opinion, here and elsewhere, is that Mazda petrol engines are well-designed and reliable. Certainly that was what my research showed, before I bought my current Mazda CX-5 with the SkyActiv-G, 165hp, 2.0-litre engine.

Nearly 40,000 miles later the car has proved totally reliable. I've spent money on regular servicing and consumables only.

Mazda diesels, however, have a poor reputation. Possibly that has been remedied in more recent examples, but it's not a risk I'd be prepared to take, and older examples I would totally avoid.

Can’t say I’ve ever heard of it. I’ve recommended these cars to many people over the years and helped source several for friends, family and work colleagues without a single case of injector issues. From a quick look online replacements aren’t hugely costly even if they were to fail. The diesels (especially the older 1.6) are another matter however. It’s a car I’d happily recommend to you but as with any used car buy on condition and history and pay extra for a good one.

You're absolutely right the issue is with the diesels - I got confused! Thanks for sorting me out on that.

Most of the issues surround Mazda diesels revolve around the 'mis-use' of cars of that engine type, i.e. predominantly short trips from cold. If you've owned such a car from new and at least do mixed driving or mainly longer distance (20 miles+ on free flowing roads) driving then not so much to worry about. Just don't turn the engine off if its doing a DPF regen and let it idle at the end of a long journey / towing for 30-60 secs to ensure the turbo cools off.

Buying a second hand one where you don't know the previous owner(s) and their driving pattern make it rather a lottery as to whether you'll inherit a car with potential expensive problems not far away.

Petrol models of the Mazda3 are reliable and rarely experience engine issues. The 3rd and 4th generation cars are all direct injection, which means they can gunk up to a degree (as can any direct injection only petrol engine) from use on predominantly short trips from cold, but nowhere near as much or as quickly as a common rail turbo diesel engined car would.

As a Mazda3 owner myself for 17 years (a 1st gen 1.6 petrol - port injected) and a member of the Mazda3 owners forum site, I've not heard of any engine problems of significance on any petrol-engined type of Mazda3. Keep it well maintained and it will last the distance.