Audi S6

The earlier generation, to 2018, runs the 4.0 V8 and is the one that most often reaches an American auction. Two turbochargers sit in the vee of the block -- complicated to service, expensive to repair, and with all the consequences of heat in a place that is hard to reach.

The later one, from 2020, is the 2.9 V6 with two turbos and 444 hp, the same unit as in the RS5 and the Panamera, with the eight-speed ZF. Very quick, but it wants uncompromising servicing: the oil galleries are temperamental and the turbos are again in the vee.

What the two share is that oil is not where to economise. On both engines the turbochargers sit between the cylinder banks, working in the hottest place and failing first when servicing has been thin.

Suspension on American cars is adaptive air. A bag or a damper damaged in a frontal impact is replaced new -- used parts for this car barely exist, and the price is among the highest in the range.

Brakes are 400 mm at the front, and the bumper hides intercoolers and oil coolers. After a frontal impact those are precisely what the yards here lack. Plus the sport rear differential, which nearly every American car carries and which wants two different oils.