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It feels as if modern cars are being endowed with ever more gear ratios. It's usually done in a bid to lower emissions – just look at Ford's 10-speed auto 'box, fitted to the Mustang, Ranger and Transit (among others) as an example of this. By offering lots of gear ratios, you eventually get to a stage where you can have exceptionally long ratios to drop engine revs right down when you're cruising, thus reducing emissions.

However, these extra gears take up space in a similar size gearbox casing, which means gearbox temperatures tend to be higher in modern gearboxes than they used to be. This extra thermal strain can lead to extra mechanical wear on gears, which in turn can mean your transmission fluid can be well past its best after 37,000 miles.