Who can blame BMW rejecting claims on engines that have been tinkered with, and how does an owner prove or not that a vehicle has or hasn't been driven hard* , common sense tells you the remaps were done for a reason and the chances are on a vehicle like the X5 it wasn't done to get more mpg.

*My last new and still current truck was a test vehicle, monitored remotely by the maker with reports forwarded to my fleet manager on a weekly basis, incredible just how much information vehicles record these days.

It doesn't sound unreasonable for BMW to refuse to pay to repair an engine that's been messed about with.

Indeed - I warned off (seemingly without success) a new (to them, it was second hand, but, if I recall, still under warranty) Mazda3 owner who wanted their 2L (120PS) engine remapped to give the performance of the 165PS version.

For some cars, like that one, if done correctly, its no problem, but I'd always be wary of doing so because, like in the BMW cases shown on this thread, the manufacturer has excellent grounds to invalidate the warranty unless the work is done via an approved outlet (rare), especially when goodwill on major engine problems often extends beyond the normal warranty period of the car.

The other issue is that often the person wanting the remap is trying to get around the extra insurance premium they would otherwise have to pay if they'd bought the uprated engine spec version of the car, and thus if that fact got back to the insurer, it would to void their policy and likely put them on a blacklist that would bump up any future premium by a significant amount, never mind open themselves up to fraud charges or serious consequences after an accident claim.

I bet this sort of thing goes on a lot these days, especially amongst the 'yoof' market, where insurance premiums are already very high.