Many of the familiar arguments for buying a diesel-powered executive saloon don’t apply to the S4 TDI. The car’s relatively low CO2 emissions do help deliver a lower showroom price for the car than its petrol-powered opponents might have, thanks to relatively low first-year VED ‘showroom tax’ banding. The way that emissions-related company car tax bands are currently set, however, means those choosing the car as a fleet option won’t be rewarded with any less benefit-in-kind liability than they would have if they’d gone for a petrol-powered rival.

You’ll also need to pay for the fuel in your car’s tank out of your own pocket, rather than as a business expense, to see the sense in picking diesel over petrol on fuel economy grounds – and you’d imagine that plenty of potential S4 owners won’t.

Rivals for the diesel S4 are thin on the ground, but it performs competitively against the Mercedes-AMG C43 and BMW 330d xDrive M Sport.

However, those who do should be very pleasantly surprised by the fuel economy that the car’s capable of. A test average of only just under 30mpg for our car may seem underwhelming – but a touring test result of better than 50mpg, representative of the car being driven at a steady 70mph, is quite remarkable for a car of this size and performance level. At that economy, the S4 could put almost 700 miles between fills of its 58-litre tank.

What Car? New car buyer marketplace - Audi A4 saloon

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