Mercedes CLS (2021)

Estimated running costs and MOT pass rates from 149 MOT tests in 2024.

Annual Cost

£2,131

£178/month

MOT Pass Rate

90%

Excellent

Road Tax

£200

Standard rate/year

Est. Insurance

Grp 30-42

2925cc Diesel

Great Choice

90% pass rate, £2,131/year to run. 8 points above average.

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Diesel2925cc5 years old149 tests26k miles avg

Annual Running Costs

Fuel (Diesel, 2925cc)

~40 mpg

£1,676

Road Tax

Standard rate (from April 2017)

£200

MOT Test

£55

Predicted Repairs

Low estimate due to excellent reliability

£200

Total per year£2,131

Per month£178/mo

Per week£41/wk

Estimates based on 7,400 miles/year (UK average), diesel at 199.33p 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

90% MOT pass rate(Excellent)

0%All-model avg: 82%100%

Excellent reliability. Very few MOT failures. That's 8 points above the average of 82% across all models in our data.

90% of MOT tests on Mercedes CLSs from 2021 ended in a pass in 2024, when they were about 3 years old. That's based on 149 tests across the UK, retests included. The average mileage recorded at those tests was 25,838 miles.

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How Does It Compare?

Rank among 2021 models2545th of 3,336(bottom 24%)

Rank among Mercedes models645th of 1,376(top half)

vs average of all models+8%(82% avg)

vs 2021 models average-2%(92% avg)

vs Mercedes average+3%(87% avg)

Mileage Analysis

25,838

Average miles

22,200

Expected for age

The average 2021 Mercedes CLS had 25,838 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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Best Year to Buy?

Of the years with at least 100 tests, the 2019 model has the highest MOT pass rate at 90%, while the 2009 model has the lowest at 78%. The 2021 scores 90%. Newer cars usually pass more often simply because they are younger, so compare years of a similar age.

Mercedes CLS by Year

Year	Pass Rate	Tests	Avg Mileage
2021	90%	149	25,838 mi
2020	85%	708	33,613 mi
2019	90%	2,938	42,687 mi
2018	89%	2,552	49,336 mi
2017	87%	3,475	61,581 mi
2016	87%	4,786	69,870 mi
2015	87%	6,871	81,130 mi
2014	85%	4,192	86,883 mi
2013	83%	7,096	95,825 mi
2012	83%	2,664	97,844 mi
2011	82%	2,675	100,976 mi
2010	79%	2,428	110,846 mi
2009	78%	2,541	114,393 mi
2008	78%	2,982	122,863 mi
2007	78%	3,915	122,774 mi
2006	79%	3,184	117,836 mi
2005	81%	1,944	108,622 mi

Similar Cars to Consider

Mercedes E

2019 · 2925cc Diesel

£2,131/year

90%

same

Ford Ranger

2019 · 3198cc Diesel

£2,281/year

87%

-3%

Audi Q5

2019 · 2967cc Diesel

£2,131/year

93%

+3%

Audi A5

2019 · 2967cc Diesel

£2,131/year

90%

same

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About the 2021 Mercedes CLS

The 2021 Mercedes CLS is a premium performance car. Our records list a 2925cc diesel engine, though engines vary between versions. 149 MOT tests were recorded on this model in 2024, making it a rare model on UK roads. It sits in the bottom 24% of 2021 models for MOT pass rate.

With an average of 25,838 miles recorded at its 2024 MOT tests, Mercedes CLS owners drive about as much as the UK average.

2021 Mercedes CLS Fuel Costs

The 2925cc 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 £1,676 per year with diesel at 199.33p per litre (GOV.UK weekly average, week of 19 October 2026; 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 Mercedes CLS?

Total estimated annual running cost is £2,131 (£178/month), broken down as £1,676 fuel, £200 road tax, £55 MOT, and £200 predicted repairs. The low repair estimate reflects the excellent 90% pass rate. These cars rarely fail their MOT, so unexpected bills are less likely.

Mercedes CLS Reliability Trend

Newer Mercedes CLSs pass their MOT more often than older ones, by 7 percentage points on average, which is mostly down to age and wear.

Buying a Used 2021 Mercedes CLS

At 5 years old, the Mercedes CLS 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 2019 model has the highest pass rate at 90%.

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.

DPF (Diesel Particulate Filter)

Watch out

Short journeys clog the DPF. Replacement costs £1,000-£2,500. Check the DPF warning light and ask about driving patterns.

Turbo Wear

Medium risk

Diesel turbos work harder and wear faster. Listen for whining noises and check for oil leaks around the turbo housing.

AdBlue System

Medium risk

Post-2015 diesels use AdBlue for emissions. Sensor failures and tank heater issues are common. Budget £200-£500 for repairs.

EGR Valve

Low risk

Exhaust Gas Recirculation valves clog with carbon deposits, causing rough running and poor economy. Cleaning costs £150-£300, replacement £300-£600.

Dual Mass Flywheel

Medium risk

Larger 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 risk

Always 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 CLS 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 CLS(2021)	90%	£1,676	£200	Grp 30-42	£2,131
Mercedes E(2019)	90%	£1,676	£200	Grp 30-42	£2,131same
Ford Ranger(2019)	87%	£1,676	£200	Grp 35-50	£2,281+£150
Audi Q5(2019)	93%	£1,676	£200	Grp 30-42	£2,131same
Audi A5(2019)	90%	£1,676	£200	Grp 30-42	£2,131same

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 CLS

Is the 2021 Mercedes CLS reliable?

Excellent reliability. Very few MOT failures. 90% of MOT tests on 2021 Mercedes CLSs ended in a pass, from 149 tests (DVSA MOT data for tests in 2024, retests included). That's 8 points above the average of 82% across all models in the same data.

How much does a 2021 Mercedes CLS cost to run?

Our estimate is £2,131 a year (£178 a month): £1,676 fuel, £200 road tax, £55 MOT and £200 predicted repairs, based on 7,400 miles a year. Insurance is not included.

What is the MOT pass rate for a 2021 Mercedes CLS?

90% of 149 MOT tests on the 2021 Mercedes CLS ended in a pass (DVSA MOT data for tests in 2024, retests included). That ranks it 2545th of 3,336 models first registered in 2021 (bottom 24%).

Which year Mercedes CLS has the best MOT pass rate?

Of the years with at least 100 tests, the 2019 Mercedes CLS has the highest MOT pass rate at 90% and the 2009 the lowest at 78%. Newer cars usually pass more often simply because they are younger and have done fewer miles.

What is the average mileage for a 2021 Mercedes CLS?

The average mileage recorded at MOT tests on the 2021 Mercedes CLS is 25,838 miles, which is in line with the expected 22,200 miles for a 3-year-old car, suggesting normal everyday use.