MERCEDES S-CLASS (2021)
Running costs, reliability data, and common problems from 164 real MOT tests.
Annual Cost
£2,042
£170/month
MOT Pass Rate
91%
Excellent
Road Tax
£195
Flat rate/year
Insurance
Grp 35-50
3982cc Petrol
Great Choice
91% pass rate, £2042/year to run. 9 points above average.
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Annual Running Costs
~30 mpg
Flat rate (post-2017)
Low estimate due to excellent reliability
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
Excellent reliability. Very few MOT failures. That's 9 points above the national average of 82%. It also outperforms the MERCEDES brand average of 87%.
At 5 years old, 91% of MERCEDES S-CLASSs from 2021 passed their MOT first time in 2026. That's based on 164 tests across the UK. The average mileage at this age is 32,036 miles.
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How Does It Compare?
Mileage Analysis
32,036
Average miles
37,000
Expected for age
The average 2021 MERCEDES S-CLASS has 32,036 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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Best Year to Buy?
The most reliable year is the 2020 model with a 95% MOT pass rate, while the 1992 model has the lowest at 72%. The 2021 sits between the two at 91%.
MERCEDES S-CLASS by Year
| Year | Pass Rate | Tests | Avg Mileage | |
|---|---|---|---|---|
| 2021 | 91% | 164 | 32,036 mi | |
| 2020 | 95% | 540 | 43,972 mi | |
| 2019 | 94% | 5,921 | 67,860 mi | |
| 2018 | 94% | 6,518 | 75,456 mi | |
| 2017 | 93% | 5,990 | 73,988 mi | |
| 2016 | 91% | 6,819 | 74,260 mi | |
| 2015 | 92% | 5,513 | 87,325 mi | |
| 2014 | 92% | 3,915 | 95,545 mi | |
| 2013 | 89% | 2,145 | 108,065 mi | |
| 2012 | 88% | 2,817 | 100,420 mi | |
| 2011 | 87% | 2,202 | 117,628 mi | |
| 2010 | 85% | 2,001 | 110,934 mi | |
| 2009 | 82% | 1,990 | 114,274 mi | |
| 2008 | 84% | 2,232 | 110,584 mi | |
| 2007 | 84% | 2,940 | 117,418 mi | |
| 2006 | 87% | 2,334 | 111,043 mi | |
| 2005 | 84% | 1,301 | 132,014 mi | |
| 2004 | 82% | 1,158 | 124,020 mi | |
| 2003 | 82% | 1,227 | 120,882 mi | |
| 2002 | 79% | 720 | 115,052 mi | |
| 2001 | 79% | 735 | 107,381 mi | |
| 2000 | 81% | 562 | 102,703 mi | |
| 1999 | 78% | 434 | 98,447 mi | |
| 1998 | 81% | 522 | 111,371 mi | |
| 1997 | 86% | 373 | 107,182 mi | |
| 1996 | 83% | 348 | 109,185 mi | |
| 1995 | 86% | 286 | 111,087 mi | |
| 1994 | 92% | 140 | 106,787 mi | |
| 1993 | 76% | 49 | 112,335 mi | |
| 1992 | 72% | 121 | 119,350 mi | |
| 1991 | 92% | 118 | 120,508 mi | |
| 1990 | 87% | 125 | 142,121 mi |
Similar Cars to Consider
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About the 2021 MERCEDES S-CLASS
The 2021 MERCEDES S-CLASS is a performance with a 3982cc petrol engine. 164 of these vehicles were MOT tested in 2026, making it a rare model on UK roads. Among all cars from 2021, the average MOT pass rate is 92%, and this model falls short of that benchmark.
With an average of 32,036 miles at 5 years old, MERCEDES S-CLASS owners drive about as much as the UK average.
2021 MERCEDES S-CLASS Fuel Costs
The 3982cc 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 S-CLASS?
Total estimated annual running cost is £2,042 (£170/month), broken down as £1592 fuel, £195 road tax, £55 MOT, and £200 predicted repairs. The low repair estimate reflects the excellent 91% pass rate. These cars rarely fail their MOT, so unexpected bills are less likely.
MERCEDES S-CLASS Reliability Trend
Newer MERCEDES S-CLASSs show better MOT pass rates than older ones, with an average improvement of 6 percentage points.
Buying a Used 2021 MERCEDES S-CLASS
At 5 years old, the MERCEDES S-CLASS offers good value with plenty of life remaining. Most manufacturer warranties will have expired, so a pre-purchase inspection is worth the cost. If you're flexible on year, the 2020 model has the highest pass rate at 95%.
Common Issues to Watch For
Based on the 2021 MERCEDES S-CLASS'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 S-CLASS stacks up against similar cars for annual running costs, insurance, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Insurance | Total/yr |
|---|---|---|---|---|---|
| MERCEDES S-CLASS(2021) | 91% | £1592 | £195 | Grp 35-50 | £2042 |
| MERCEDES C(2019) | 91% | £1592 | £190 | Grp 35-50 | £2037-£5 |
| PORSCHE CAYENNE(2019) | 95% | £1592 | £190 | Grp 35-50 | £2037-£5 |
| PORSCHE 911(2019) | 97% | £1592 | £190 | Grp 35-50 | £2037-£5 |
| AUDI A6(2020) | 94% | £1592 | £190 | Grp 35-50 | £2037-£5 |
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
MERCEDES C
2019 · 3982cc Petrol
PORSCHE CAYENNE
2019 · 3996cc Petrol
PORSCHE 911
2019 · 3996cc Petrol
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