AUDI A8 S LINE 50TDI MHEV QUATTRO A (2021)
Running costs, reliability data, and common problems from 30 real MOT tests.
Annual Cost
£1,845
£154/month
MOT Pass Rate
87%
Good
Road Tax
£195
Flat rate/year
Insurance
Grp 30-42
2967cc Diesel
Solid Option
87% pass rate, £1845/year to run. 5 points above average.
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Annual Running Costs
~40 mpg
Flat rate (post-2017)
Based on 7,400 miles/year (UK average), current fuel prices, and repair likelihood from MOT data. Insurance not included.
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Reliability Verdict
Good reliability. Occasional issues but generally solid. That's close to the national average of 82%.
At 5 years old, 87% of AUDI A8 S LINE 50TDI MHEV QUATTRO As from 2021 passed their MOT first time in 2026. That's based on 30 tests across the UK. The average mileage at this age is 33,546 miles.
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How Does It Compare?
Mileage Analysis
33,546
Average miles
37,000
Expected for age
The average 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A has 33,546 miles on the clock, which is in line with the expected 37,000 miles for a 5-year-old car, suggesting normal everyday use.
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About the 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A
The 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A is a premium performance with a 2967cc diesel engine. 30 of these vehicles were MOT tested in 2026, making it a rare model on UK roads. It sits in the bottom 90% of 2021 cars for MOT pass rates.
With an average of 33,546 miles at 5 years old, AUDI A8 S LINE 50TDI MHEV QUATTRO A owners drive about as much as the UK average.
2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A Fuel Costs
The 2967cc diesel engine is on the larger side, so fuel won't be this car's strong point. Expect around 40 mpg in mixed driving, which works out to roughly £1,245 per year at current diesel prices of 148p per litre (based on 7,400 miles per year). Diesel cars of this age should have their DPF (diesel particulate filter) checked, as replacements can be costly.
What does it cost to own a 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A?
Total estimated annual running cost is £1,845 (£154/month), broken down as £1245 fuel, £195 road tax, £55 MOT, and £350 predicted repairs. Repair costs are moderate, reflecting the 87% pass rate. Keeping on top of servicing will help avoid surprises.
Buying a Used 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A
At 5 years old, the AUDI A8 S LINE 50TDI MHEV QUATTRO A offers good value with plenty of life remaining. Most manufacturer warranties will have expired, so a pre-purchase inspection is worth the cost. Note: with only 30 tests in our data, these figures should be treated as indicative rather than definitive.
Common Issues to Watch For
Based on the 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A's fuel type, age, and engine size, these are the most likely problem areas to check.
DPF (Diesel Particulate Filter)
Watch outShort journeys clog the DPF. Replacement costs £1,000-£2,500. Check the DPF warning light and ask about driving patterns.
Turbo Wear
Medium riskDiesel turbos work harder and wear faster. Listen for whining noises and check for oil leaks around the turbo housing.
AdBlue System
Medium riskPost-2015 diesels use AdBlue for emissions. Sensor failures and tank heater issues are common. Budget £200-£500 for repairs.
EGR Valve
Low riskExhaust Gas Recirculation valves clog with carbon deposits, causing rough running and poor economy. Cleaning costs £150-£300, replacement £300-£600.
Dual Mass Flywheel
Medium riskLarger diesel engines put extra strain on the dual mass flywheel. Listen for rattling at idle. Replacement with clutch is £800-£1,500.
Service History
Low riskAlways request a full service history. Regular servicing is the single best indicator of how well a car has been maintained, regardless of mileage.
Running Costs Compared
How the 2021 AUDI A8 S LINE 50TDI MHEV QUATTRO A stacks up against similar cars for annual running costs, insurance, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Insurance | Total/yr |
|---|---|---|---|---|---|
| AUDI A8 S LINE 50TDI MHEV QUATTRO A(2021) | 87% | £1245 | £195 | Grp 30-42 | £1845 |
| MERCEDES E(2019) | 90% | £1245 | £190 | Grp 30-42 | £1690-£155 |
| FORD RANGER(2019) | 87% | £1245 | £190 | Grp 35-50 | £1840-£5 |
| AUDI Q5(2019) | 93% | £1245 | £190 | Grp 30-42 | £1690-£155 |
| AUDI A5(2019) | 90% | £1245 | £190 | Grp 30-42 | £1690-£155 |
Estimates based on 7,400 miles/year, current fuel prices, and MOT data. Insurance groups are indicative. Actual costs vary by driver, location, and usage.
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