Mercedes 420 (1990)

Estimated running costs and MOT pass rates from 125 MOT tests in 2024.

Annual Cost

£2,888

£241/month

MOT Pass Rate

74%

Average

Road Tax

£375

Estimated/year

Est. Insurance

Grp 35-50

4196cc Petrol

Check Carefully

74% pass rate, £2,888/year to run. 8 points below average.

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Petrol4196cc36 years old125 tests131k miles avg

Annual Running Costs

Fuel (Petrol, 4196cc)

~30 mpg

£1,958

Road Tax

Pre-2001 engine size rate

£375

MOT Test

£55

Predicted Repairs

Higher estimate due to low pass rate

£500

Total per year£2,888

Per month£241/mo

Per week£56/wk

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.

Reliability Verdict

74% MOT pass rate(Average)

0%All-model avg: 82%100%

Average reliability. Expect some repairs as it ages. That's 8 points below the average of 82% across all models in our data. It falls below the Mercedes brand average of 87%.

74% of MOT tests on Mercedes 420s from 1990 ended in a pass in 2024, when they were about 34 years old. That's based on 125 tests across the UK, retests included. The average mileage recorded at those tests was 131,208 miles.

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How Does It Compare?

Rank among 1990 models141st of 182(bottom 24%)

Rank among Mercedes models1264th of 1,376(bottom 9%)

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

vs 1990 models average-5%(79% avg)

vs Mercedes average-13%(87% avg)

Mileage Analysis

131,208

Average miles

251,600

Expected for age

The average 1990 Mercedes 420 had 131,208 miles on the clock at its 2024 MOT, which is below the expected 251,600 miles for a 34-year-old car. This suggests lighter use than average, which generally means less wear on major components.

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Mercedes 420 by Year

Year	Pass Rate	Tests	Avg Mileage
1991	77%	44	131,577 mi
1990	74%	125	131,208 mi

Similar Cars to Consider

Jaguar XJS

1992 · 4000cc Petrol

£2,888/year

78%

+4%

Land Rover Range Rover

1992 · 3950cc Petrol

£2,738/year

85%

+11%

TVR Griffith

1992 · 3948cc Petrol

£2,738/year

88%

+14%

Jaguar XJ

1992 · 3980cc Petrol

£2,738/year

82%

+8%

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About the 1990 Mercedes 420

The 1990 Mercedes 420 is a premium performance car. Our records list a 4196cc petrol engine, though engines vary between versions. 125 MOT tests were recorded on this model in 2024, making it a rare model on UK roads. It sits in the bottom 24% of 1990 models for MOT pass rate.

With an average of 131,208 miles recorded at its 2024 MOT tests, Mercedes 420 owners tend to use this car less than the typical driver.

1990 Mercedes 420 Fuel Costs

The 4196cc 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 1990 Mercedes 420?

Total estimated annual running cost is £2,888 (£241/month), broken down as £1,958 fuel, £375 road tax, £55 MOT, and £500 predicted repairs. Repair costs are moderate, reflecting the 74% pass rate. Keeping on top of servicing will help avoid surprises.

Buying a Used 1990 Mercedes 420

At 36 years old, the Mercedes 420 is firmly in budget territory. Purchase prices are low, but check for rust, worn suspension bushes, and electrical gremlins. A full service history is especially valuable at this age.

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.

Timing Chain / Belt

Watch out

At 36 years old, check whether the timing belt has been replaced (typically due every 5-7 years or 60,000-100,000 miles). A snapped belt can destroy the engine.

Oil Consumption

Medium risk

Larger petrol engines can develop higher oil consumption as they age. Check the oil level and look for blue smoke from the exhaust.

Rust and Corrosion

Watch out

At 10+ years, check wheel arches, sills, subframe, and brake lines for rust. Structural corrosion is an MOT failure. Prevention is far cheaper than repair.

Suspension Bushings

Watch out

Rubber suspension bushes harden and crack with age, causing knocking noises and vague handling. A full refresh costs £300-£800 depending on the car.

Clutch Wear

Watch out

With an average of 131k miles, clutch replacement may be due (typical lifespan 60,000-100,000 miles). Budget £400-£800 for a new clutch kit.

Brake Discs and Pads

Medium risk

High-mileage cars often need brake disc replacement, not just pads. A full set of discs and pads costs £200-£500 per axle.

Engine Mounts

Medium risk

Worn engine mounts cause excessive vibration and movement. Replacement costs £150-£400 per mount. Check for vibration at idle with the bonnet open.

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 1990 Mercedes 420 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 420(1990)	74%	£1,958	£375	Grp 35-50	£2,888
Jaguar XJS(1992)	78%	£1,958	£375	Grp 35-50	£2,888same
Land Rover Range Rover(1992)	85%	£1,958	£375	Grp 35-50	£2,738-£150
TVR Griffith(1992)	88%	£1,958	£375	Grp 35-50	£2,738-£150
Jaguar XJ(1992)	82%	£1,958	£375	Grp 35-50	£2,738-£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 1990 Mercedes 420

Is the 1990 Mercedes 420 reliable?

Average reliability. Expect some repairs as it ages. 74% of MOT tests on 1990 Mercedes 420s ended in a pass, from 125 tests (DVSA MOT data for tests in 2024, retests included). That's 8 points below the average of 82% across all models in the same data.

How much does a 1990 Mercedes 420 cost to run?

Our estimate is £2,888 a year (£241 a month): £1,958 fuel, £375 road tax, £55 MOT and £500 predicted repairs, based on 7,400 miles a year. Insurance is not included.

What is the MOT pass rate for a 1990 Mercedes 420?

74% of 125 MOT tests on the 1990 Mercedes 420 ended in a pass (DVSA MOT data for tests in 2024, retests included). That ranks it 141st of 182 models first registered in 1990 (bottom 24%).

What is the average mileage for a 1990 Mercedes 420?

The average mileage recorded at MOT tests on the 1990 Mercedes 420 is 131,208 miles, which is below the expected 251,600 miles for a 34-year-old car. This suggests lighter use than average, which generally means less wear on major components.