Audi SQ8 TDI

Scope of this guide

This guide is scoped to the Audi SQ8 TDI, the SUV-coupe with the 4.0L V8 twin-turbo diesel (TDI) with electric compressor, mild hybrid engine, all-wheel drive and an eight-speed automatic gearbox, as sold in the UK and Europe from 2019 until the diesel was withdrawn in 2020. It is not a guide to the SQ8 TFSI that replaced it, which has a 4.0 litre petrol V8 with 507 PS and 770 Nm, to the later facelifted petrol SQ8, to the RS Q8, or to the SQ7 TDI, which shares the engine in a different body. Where those cars differ we say so below, because an advert that says only "SQ8 V8" can describe either fuel.

We have not driven this model for this article. Everything here comes from three cited sources: Audi Australia's own magazine page announcing the car (7 February 2020), PistonHeads' UK first drive of 10 October 2019, and the government recall checker. We did not run the recall checker for any particular car, because this guide is not about one vehicle. You should run it yourself on the registration of any car you are considering. We also read GTspirit's launch report (22 June 2019), evo's launch report (21 June 2019), a PistonHeads footnote on the diesel being dropped (15 July 2020), Car Throttle's report on the petrol replacement and Audi's own SQ8 TFSI page, and we flag points that rest on them. Prices are history, not valuations.

The figures at a glance

• Engine: 4.0L V8 twin-turbo diesel (TDI) with electric compressor, mild hybrid. PistonHeads prints 3,956cc. Our catalogue previously held 3996 cc, which is the displacement of the later petrol SQ8 TFSI, so we have corrected it to 3956 cc.
• Power: 435 PS, which Audi Australia prints as 320 kW. Converted, 435 PS is about 429 bhp (435 x 0.98632) and 320 kW is about 429 bhp (320 x 1.34102). Evo printed 429 bhp directly. PistonHeads printed 435hp for peak power at 3,750 to 5,000 rpm, which is the metric figure with a different unit label. We state 429 bhp as the converted catalogue figure.
• Torque: 900 Nm, which is 664 lb ft on PistonHeads and evo (900 Nm is about 663.8 lb ft). Audi Australia gives 900 Nm from 1,250 to 3,250 rpm. PistonHeads gives the plateau as starting at 1,000 rpm, so the lower end of the band differs between sources.
• 0-100 km/h: 4.8 seconds. PistonHeads prints 4.8 seconds for 0-62 mph, which is the same distance in practice because 100 km/h is about 62.1 mph, and Audi Australia prints 4.8 seconds for 0 to 100 km/h. These are manufacturer claims, not our measurements.
• Top speed: 250 km/h, electronically governed. PistonHeads prints 155 mph, which converts to about 249 km/h and is the same limiter.
• Drive: all-wheel drive through Audi's quattro system. PistonHeads calls it four-wheel drive and Audi Australia says power goes to all four wheels.
• Gearbox: eight-speed automatic, which Audi calls tiptronic.
• Weight: 2,365 kg unladen on PistonHeads. Evo says only that it weighs well over two tonnes.
• Official economy: 31.4 mpg and 205 g/km of CO2 on PistonHeads, with the Vorsprung at 30.7 mpg. Audi Australia prints 7.8 L/100km and the same 205 g/km, and the two fuel figures do not match because they come from different markets and test set-ups.

How the engine works

Audi's V8 diesel is the part of this car that makes it different from the 3.0 TDI Q8. Two turbochargers do the main work, and an electric powered compressor sits behind the intercooler to fill the gap while the turbos spool up. According to Audi Australia, GTspirit and evo, that compressor and the mild-hybrid system run from a 48-volt electrical system. GTspirit says a belt alternator recovers energy, and evo says the same 48V system also feeds the active anti-roll bars. An Audi technical summary we saw only as a search snippet puts the compressor at a maximum of 7 kW, and we have not verified that number from the page itself.

For an owner this means the car has more electrical hardware than a plain diesel V8 would: a 48V battery, a belt alternator that recovers energy, the compressor and the active chassis components all depend on that system. We found no source that lists failures, so we cannot tell you what goes wrong or how often. What we can say is that these are the parts a specialist should check for stored fault codes before you buy.

What the car is like to live with

PistonHeads' Sam Sheehan drove a Vorsprung on standard 22-inch wheels and wrote that it did not exactly waft. In his words, large bumps are dealt with well, but smaller, sharper imperfections make for a busy ride, and he switched back to comfort mode. He also noticed a step in performance at about 2,000 rpm, which he partly put down to the gearbox in town. GTspirit's launch report says 21-inch wheels were standard, so the wheel size on a car you are viewing may not match the figure we quote, and wheel size will change both ride and tyre cost.

GTspirit also lists adaptive air suspension as standard, with four-wheel steering, a sport differential and an electromechanical active anti-roll bar as options. Cars therefore differ widely in what they carry. Check the build sheet or the window sticker rather than assuming a car has the options from the road test. PistonHeads says a tyre pressure monitoring system was a 325 pound option on the test car, which is a reminder that not every feature was standard.

When it was sold, and when it stopped

Audi unveiled the SQ8 TDI in June 2019. GTspirit expected a price of about 100,000 euros, evo expected UK cars by the end of that summer from around 80,000 pounds, and PistonHeads' October 2019 test lists 81,740 pounds for the base car and 104,240 pounds for the Vorsprung as tested with options. Audi Australia announced its own pricing and an April arrival on 7 February 2020.

The diesel was short-lived in Europe. PistonHeads reported on 15 July 2020 that the SQ7 and SQ8 would from then on be sold with the biturbo 4.0 V8 TFSI, which makes 72hp more than the diesel but has less torque, and it warned that the petrol would not match the diesel's fuel economy or its in-gear shove. Car Throttle's report puts the petrol cars on UK sale in autumn 2020. That is why we end this guide in 2020. Other markets kept the diesel longer: search summaries of Australian reports suggest it carried on there until 2022, but we could not read those pages and we have not relied on them. Our previous catalogue end year of 2024 is not supported by any source we read, so we changed it.

Buying advice

Nobody at Dream Car Garage has inspected a used example, and none of the sources we read covers reliability, service intervals or parts costs, so this section is our reasoning, not reported fact.

• Confirm it is a diesel. The petrol SQ8 TFSI looks almost the same from the outside, and the badge on the tailgate does not tell you the fuel. Check the V5C and the engine code, and the official CO2 figure should be near 205 g/km on a TDI.
• Ask for a full service history from an Audi dealer or a specialist who works on mild-hybrid cars, and ask whether the 48V system has ever been diagnosed.
• Check the emissions equipment. Modern diesels carry particulate filters and exhaust fluid systems. Ask when the filter was last cleared, and ask if the car has had short-trip use, which is hard on them.
• Look at the tyres and wheels. This is a car of over two tonnes on large wheels, and wide tyres are costly.
• Test the air suspension through its full height range, test the four-wheel steering if fitted, and listen for noises from the active anti-roll bars.
• Run the government recall checker on the registration, and ask the seller for any recall paperwork. We did not run it for this article.

What the SQ8 TDI is, in short

It is a heavy, fast, diesel V8 SUV-coupe with 429 bhp and 900 Nm that claims 0-100 km/h in 4.8 seconds before reaching 250 km/h at the limiter. It is a short-run car, sold in Europe for roughly a year before Audi swapped the engine for petrol. That makes it a distinct choice among the SQ8 generation, and it also means the diesel-specific hardware has a thin body of owner experience behind it. We would pay for a specialist inspection before committing.

About the photograph

The hero image is a photograph of a black 2019 Audi SQ8 Vorsprung TDI taken in Warwick on 17 October 2020 by Vauxford and published on Wikimedia Commons under CC BY-SA 4.0. We cropped it to a widescreen format and resized it. The number plate in the original file was already covered by a blank panel, and we did not edit it.