The point about the kind of miles is worth expanding, because it does a lot of work here.
Motorway miles are gentle. Constant speed, engine at temperature, few cold starts, minimal braking, no stop-start clutch work. A car with ninety thousand of those can be in better mechanical condition than one with thirty thousand short urban trips.
Short cold trips are the harshest use there is. The engine never fully warms, oil dilutes with fuel, condensation accumulates in the exhaust and the oil, and diesel particulate filters in particular never regenerate properly.
So the questions to ask are not how many miles but what kind:
- What was it used for, and by whom
- How far was the daily journey
- Was it ever mostly at motorway speeds
A fleet or company car doing long trips is frequently a good buy despite the number, and this is the segment where the price drop is largest relative to the actual condition.
On the low-mileage car, the equivalent question is how it was stored and whether it was run. A car started once a fortnight for a short trip has had nine years of the worst possible use pattern in miniature. A car genuinely laid up and properly recommissioned is a different thing again.