MERCEDES SL 400 GRAND EDITION AUTO (2021)
Running costs, reliability data, and common problems from 34 real MOT tests.
Annual Cost
£2,192
£183/month
MOT Pass Rate
85%
Good
Road Tax
£195
Flat rate/year
Insurance
Grp 30-42
2996cc Petrol
Solid Option
85% pass rate, £2192/year to run. Close to the national average.
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Annual Running Costs
~30 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, 85% of MERCEDES SL 400 GRAND EDITION AUTOs from 2021 passed their MOT first time in 2026. That's based on 34 tests across the UK. The average mileage at this age is 18,981 miles.
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How Does It Compare?
Mileage Analysis
18,981
Average miles
37,000
Expected for age
The average 2021 MERCEDES SL 400 GRAND EDITION AUTO has 18,981 miles on the clock, which is below the expected 37,000 miles for a 5-year-old car. This suggests lighter use than average, which generally means less wear on major components.
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MERCEDES SL 400 GRAND EDITION AUTO by Year
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About the 2021 MERCEDES SL 400 GRAND EDITION AUTO
The 2021 MERCEDES SL 400 GRAND EDITION AUTO is a large car with a 2996cc petrol engine. 34 of these vehicles were MOT tested in 2026, making it a rare model on UK roads. It sits in the bottom 93% of 2021 cars for MOT pass rates.
With an average of 18,981 miles at 5 years old, MERCEDES SL 400 GRAND EDITION AUTO owners tend to use this car less than the typical driver.
2021 MERCEDES SL 400 GRAND EDITION AUTO Fuel Costs
The 2996cc petrol engine is on the larger side, so fuel won't be this car's strong point. Expect around 30 mpg in mixed driving, which works out to roughly £1,592 per year at current petrol prices of 142p per litre (based on 7,400 miles per year).
What does it cost to own a 2021 MERCEDES SL 400 GRAND EDITION AUTO?
Total estimated annual running cost is £2,192 (£183/month), broken down as £1592 fuel, £195 road tax, £55 MOT, and £350 predicted repairs. Repair costs are moderate, reflecting the 85% pass rate. Keeping on top of servicing will help avoid surprises.
Buying a Used 2021 MERCEDES SL 400 GRAND EDITION AUTO
At 5 years old, the MERCEDES SL 400 GRAND EDITION AUTO 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 34 tests in our data, these figures should be treated as indicative rather than definitive.
Common Issues to Watch For
Based on the 2021 MERCEDES SL 400 GRAND EDITION AUTO's fuel type, age, and engine size, these are the most likely problem areas to check.
Oil Consumption
Low riskLarger petrol engines can develop higher oil consumption as they age. Check the oil level and look for blue smoke from the exhaust.
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 MERCEDES SL 400 GRAND EDITION AUTO stacks up against similar cars for annual running costs, insurance, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Insurance | Total/yr |
|---|---|---|---|---|---|
| MERCEDES SL 400 GRAND EDITION AUTO(2021) | 85% | £1592 | £195 | Grp 30-42 | £2192 |
| BMW 5 SERIES(2019) | 92% | £1592 | £190 | Grp 30-42 | £2037-£155 |
| BMW X3(2019) | 92% | £1592 | £190 | Grp 30-42 | £2037-£155 |
| MERCEDES GLC(2019) | 93% | £1592 | £190 | Grp 30-42 | £2037-£155 |
| BMW X5(2019) | 92% | £1592 | £190 | Grp 30-42 | £2037-£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.
Related Mercedes Models
Explore other Mercedes cars or similar models in the same category.
MERCEDES A
2019 · 1461cc Diesel
MERCEDES C
2017 · 1991cc Hybrid
MERCEDES A-CLASS
2017 · 1461cc Diesel
BMW 5 SERIES
2019 · 2998cc Petrol
BMW X3
2019 · 2998cc Petrol
MERCEDES GLC
2019 · 2996cc Petrol
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