Mercedes S 350 L AMG Line Premium + D A (2021)

Estimated running costs and MOT pass rates from 161 MOT tests in 2024.

Annual Cost

£2,131

£178/month

MOT Pass Rate

96%

Excellent

Road Tax

£200

Standard rate/year

Est. Insurance

Grp 30-42

2925cc Diesel

Great Choice

96% pass rate, £2,131/year to run. 14 points above average.

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£4.99

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Diesel2925cc5 years old161 tests35k 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

96% MOT pass rate(Excellent)

0%All-model avg: 82%100%

Excellent reliability. Very few MOT failures. That's 14 points above the average of 82% across all models in our data. It also outperforms the Mercedes brand average of 87%.

96% of MOT tests on Mercedes S 350 L AMG Line Premium + D As from 2021 ended in a pass in 2024, when they were about 3 years old. That's based on 161 tests across the UK, retests included. The average mileage recorded at those tests was 35,442 miles.

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How Does It Compare?

Rank among 2021 models114th of 3,336(top 4%)

Rank among Mercedes models58th of 1,376(top 5%)

vs average of all models+14%(82% avg)

vs 2021 models average+4%(92% avg)

vs Mercedes average+9%(87% avg)

Mileage Analysis

35,442

Average miles

22,200

Expected for age

The average 2021 Mercedes S 350 L AMG Line Premium + D A had 35,442 miles on the clock at its 2024 MOT, which is well above the expected 22,200 miles for a 3-year-old car. Check service history carefully, as high-mileage cars need consistent maintenance to stay reliable.

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Similar Cars to Consider

Mercedes E

2019 · 2925cc Diesel

£2,131/year

90%

-6%

Ford Ranger

2019 · 3198cc Diesel

£2,281/year

87%

-9%

Audi Q5

2019 · 2967cc Diesel

£2,131/year

93%

-3%

Audi A5

2019 · 2967cc Diesel

£2,131/year

90%

-6%

Check a Specific Mercedes S 350 L AMG Line Premium + D A

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About the 2021 Mercedes S 350 L AMG Line Premium + D A

The 2021 Mercedes S 350 L AMG Line Premium + D A is a premium performance car. Our records list a 2925cc diesel engine, though engines vary between versions. 161 MOT tests were recorded on this model in 2024, making it a rare model on UK roads. It ranks in the top 4% of all 2021 models for MOT pass rate.

With an average of 35,442 miles recorded at its 2024 MOT tests, Mercedes S 350 L AMG Line Premium + D A owners cover more miles than the average driver. High-mileage examples should be checked carefully for wear on suspension, brakes, and drivetrain components.

2021 Mercedes S 350 L AMG Line Premium + D A 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 S 350 L AMG Line Premium + D A?

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 96% pass rate. These cars rarely fail their MOT, so unexpected bills are less likely.

Buying a Used 2021 Mercedes S 350 L AMG Line Premium + D A

At 5 years old, the Mercedes S 350 L AMG Line Premium + D A offers good value with plenty of life remaining. Most manufacturer warranties will have expired, so a pre-purchase inspection is worth the cost.

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 S 350 L AMG Line Premium + D A 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 S 350 L AMG Line Premium + D A(2021)	96%	£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 S 350 L AMG Line Premium + D A

Is the 2021 Mercedes S 350 L AMG Line Premium + D A reliable?

Excellent reliability. Very few MOT failures. 96% of MOT tests on 2021 Mercedes S 350 L AMG Line Premium + D As ended in a pass, from 161 tests (DVSA MOT data for tests in 2024, retests included). That's 14 points above the average of 82% across all models in the same data.

How much does a 2021 Mercedes S 350 L AMG Line Premium + D A 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 S 350 L AMG Line Premium + D A?

96% of 161 MOT tests on the 2021 Mercedes S 350 L AMG Line Premium + D A ended in a pass (DVSA MOT data for tests in 2024, retests included). That ranks it 114th of 3,336 models first registered in 2021 (top 4%).

What is the average mileage for a 2021 Mercedes S 350 L AMG Line Premium + D A?

The average mileage recorded at MOT tests on the 2021 Mercedes S 350 L AMG Line Premium + D A is 35,442 miles, which is well above the expected 22,200 miles for a 3-year-old car. Check service history carefully, as high-mileage cars need consistent maintenance to stay reliable.