Mike, they didnt say why it was more than the 12000 service, as far as I am aware there isnt a lot of difference between the 12000 and 24000 service. I do remember reading that they do a road test on the 24000 service though. I am going to make sure I note down the mileage, I would have thought a couple of miles is sufficient for a road test? Also Im going to mark the oil filter etc to make sure that they get changed. Ive also asked them to sort out my 4000rpm rattle/resonance and stated that I asked them to fix this at the 12000 service (which they couldnt do as they didnt have enough staff at the time). I asked if it would be covered under warranty and they said they didnt know until they took a look. It was the service manager I spoke to so why didnt he just come out with it and say, oh yes thats a common fault with 172s, its probably the exhaust mid section. Ive had this problem since day one but have put up with it upto now.