Broken piston in Mini R56 - wear and tear or manufacturing fault?

I have a 2007 Mini Cooper S which has done around 62,000 miles. Last week, it began running very roughly and was noticeably lacking in power. I took it to a Mini dealer who noted that there was no compression occurring in cylinder three. They have now (at a labour cost of some £1700) dismantled the engine to find the cause of the problem. This has shown that the number three cylinder piston has broken, along with its ring. The total cost for repair will be around £3500. I asked the dealer if this was a fault to be expected in a car of this age and mileage (which has been serviced to manufacturer's schedule at main dealers through its life). They answered that they could not remember seeing any similar problems before, and agreed to contact BMW to ask for a goodwill contribution to costs since this would seem likely to be a material/manufacturing failure. However, BMW replied that they would not bear any of the cost owing to the age of the car. Only a year ago I had a large bill for repair in the same car owing to timing chain failure (which I understand is a well-recognised failing on this engine); on this occasion, BMW did make a partial contribution to costs. Despite this being pointed out to them (two significant engine faults in a well-maintained car), they have declined to bear any of the cost of repair for this new major engine failure. I would be grateful for your opinion on whether a piston breaking in a well-maintained car of low to average mileage should be considered to be a failure in material or manufacturing and hence if it is reasonable to expect the maker to bear any responsibility for such a failure?
In my opinion, these sorts of failures are largely due to the 'TLC' oil service regime that can leave the engine running in the same oil for 20,000 miles. My advice has always been to change the oil and filter at least every year or every 10,000 miles whichever comes first.
Answered by Honest John on

Ask Honest John