Mercedes SL 400 Grand Edition Auto (2021)
Estimated running costs and MOT pass rates from 34 MOT tests in 2024.
Annual Cost
£2,563
£214/month
MOT Pass Rate
85%
Good
Road Tax
£200
Standard rate/year
Est. Insurance
Grp 30-42
2996cc Petrol
Solid Option
85% pass rate, £2,563/year to run. Close to the average across all models.
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Annual Running Costs
~30 mpg
Standard rate (from April 2017)
Estimates based on 7,400 miles/year (UK average), petrol at 174.57p a litre (GOV.UK weekly average, week of 19 October 2026), GOV.UK road tax rates and repair likelihood from MOT data. Insurance not included. Cars registered from April 2017 pay the £200 standard rate, plus £440 a year for five years (from the second year) if they cost over £40,000 new (over £50,000 for electric cars).
Reliability Verdict
Good reliability. Occasional issues but generally solid. That's close to the average of 82% across all models in our data.
85% of MOT tests on Mercedes SL 400 Grand Edition Autos from 2021 ended in a pass in 2024, when they were about 3 years old. That's based on 34 tests across the UK, retests included. The average mileage recorded at those tests was 18,981 miles.
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How Does It Compare?
Mileage Analysis
18,981
Average miles
22,200
Expected for age
The average 2021 Mercedes SL 400 Grand Edition Auto had 18,981 miles on the clock at its 2024 MOT, which is in line with the expected 22,200 miles for a 3-year-old car, suggesting normal everyday use.
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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 premium performance car. Our records list a 2996cc petrol engine, though engines vary between versions. 34 MOT tests were recorded on this model in 2024, making it a rare model on UK roads. It sits in the bottom 7% of 2021 models for MOT pass rate.
With an average of 18,981 miles recorded at its 2024 MOT tests, Mercedes SL 400 Grand Edition Auto owners drive about as much as the UK average.
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 £1,958 per year with petrol at 174.57p per litre (GOV.UK weekly average, week of 19 October 2026; 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 £2,563 (£214/month), broken down as £1,958 fuel, £200 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
These are typical issues for cars of this age, fuel type and engine size, not faults recorded on this model's MOT tests. Use them as a checklist when you view one.
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 estimated annual running costs, insurance group, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Est. Ins. Group | Total/yr |
|---|---|---|---|---|---|
| Mercedes SL 400 Grand Edition Auto(2021) | 85% | £1,958 | £200 | Grp 30-42 | £2,563 |
| BMW 5 Series(2019) | 92% | £1,958 | £200 | Grp 30-42 | £2,413-£150 |
| BMW X3(2019) | 92% | £1,958 | £200 | Grp 30-42 | £2,413-£150 |
| Mercedes GLC(2019) | 93% | £1,958 | £200 | Grp 30-42 | £2,413-£150 |
| BMW X5(2019) | 92% | £1,958 | £200 | Grp 30-42 | £2,413-£150 |
Estimates based on 7,400 miles/year, GOV.UK average pump prices for the week of 19 October 2026, GOV.UK road tax rates and MOT data. Insurance groups are our rough estimate from engine size, not official groups. Actual costs vary by driver, location, and usage.
Questions about the 2021 Mercedes SL 400 Grand Edition Auto
Is the 2021 Mercedes SL 400 Grand Edition Auto reliable?
Good reliability. Occasional issues but generally solid. 85% of MOT tests on 2021 Mercedes SL 400 Grand Edition Autos ended in a pass, from 34 tests (DVSA MOT data for tests in 2024, retests included). That's 3 points above the average of 82% across all models in the same data.
How much does a 2021 Mercedes SL 400 Grand Edition Auto cost to run?
Our estimate is £2,563 a year (£214 a month): £1,958 fuel, £200 road tax, £55 MOT and £350 predicted repairs, based on 7,400 miles a year. Insurance is not included.
What is the MOT pass rate for a 2021 Mercedes SL 400 Grand Edition Auto?
85% of 34 MOT tests on the 2021 Mercedes SL 400 Grand Edition Auto ended in a pass (DVSA MOT data for tests in 2024, retests included). That ranks it 3111th of 3,336 models first registered in 2021 (bottom 7%).
What is the average mileage for a 2021 Mercedes SL 400 Grand Edition Auto?
The average mileage recorded at MOT tests on the 2021 Mercedes SL 400 Grand Edition Auto is 18,981 miles, which is in line with the expected 22,200 miles for a 3-year-old car, suggesting normal everyday use.
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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