This is a known problem in the Mazda turbo-diesel, and many owners have suffered similar failures. The problem begins with the formation of hard, carbon deposits in the top end of the engine which eventually find their way into the engine’s sump and block the oil pick-up. When that happens, the engine can’t pump oil efficiently and some parts of the engine become oil-starved. That’s when a build-up of friction and, therefore, heat, will cause a catastrophic failure with the attendant metal shavings that were subsequently discovered in your engine.

So why was the problem missed? An enthusiastic mechanic will always have a look at the oil that comes out of an engine, looking for just the symptoms you’ve noted. A really keen technician will sometimes even cut the old oil filter open to check for anything that shouldn’t be there. Unfortunately, in the context of a busy workshop with price-conscious customers, this doesn’t always happen. In the Mazda’s engine, the normal practice should be to check the strainer that covers the oil pick-up, but, again, that may not have been the case with your engine. If the workshop you used was a Mazda dealership, I’d be asking management why that process wasn’t followed. Even then, it’s difficult to say whether this check would have saved your engine, as the damage may already have been done.

The tyre guys are correct that carmakers set their pressures based on a blend of performance, economy, comfort and wear. Tyre companies generally advise that you run higher tyre pressures for better performance and economy, but that will compromise the ride comfort. I would run a higher pressure for the benefits to handling and fuel consumption. Make sure you rotate your tyres regularly, that will even out the wear over the life of the tyres.

Stick to the well-proven Japanese brands, such as the Mazda 6, Honda Accord, and perhaps the Korean Kia Cerato. As a private sale your Mazda would be worth $11,000-$12,000, as a trade-in $8000-$10,000.