That's interesting because I have run both of these cars for extended periods: www.honestjohn.co.uk/our-cars/mazda-6-22d-se-l-nav.../ and www.honestjohn.co.uk/our-cars/volvo-s60/

The fuel in oil problem can arise with the Mazda if 10,000 mile oil changes and regular checks of the dispstick are not adhered to. This is because of the amount of diesel the system adds to the engine to actively regenerate the DPF without requiring AdBlue.

The Volvo uses different technology. Its handling is okay but not quite in the same class as the Mazda. Mine was on 50 section 17-inch tyres rather than the 55 section 17s of thew Mazda, but ride was not too badly affected. I didn't notice excess tyre wear. But I would not go for 18-inch or 19-inch wheels on either car.