Is the 2018 MERCEDES S-CLASS reliable?

Excellent reliability. Very few MOT failures. 94% of MERCEDES S-CLASSs from 2018 passed their MOT first time in 2026, based on 6,518 tests. That's 12 points above the national average of 82%.

How much does a 2018 MERCEDES S-CLASS cost to run?

Estimated annual running cost is £2,042 (£170/month), including £1592 fuel, £195 road tax, £55 MOT, and £200 predicted repairs.

What is the MOT pass rate for a 2018 MERCEDES S-CLASS?

The 2018 MERCEDES S-CLASS has a 94% MOT pass rate based on 6,518 tests in 2026. This ranks 128 out of 649 cars from 2018.

Which year MERCEDES S-CLASS is most reliable?

The 2020 MERCEDES S-CLASS has the highest MOT pass rate at 95%. The least reliable year is 1992 at 72%.

MERCEDES S-CLASS (2018)

Q: What is the average mileage for a 2018 MERCEDES S-CLASS?

The average mileage for a 2018 MERCEDES S-CLASS is 75,456 miles, which is above the expected 59,200 miles for a 8-year-old car. Higher-mileage cars often have more motorway miles, which is generally less harmful than stop-start urban driving.

Running costs, reliability data, and common problems from 6,518 real MOT tests.

Annual Cost

£2,042

£170/month

MOT Pass Rate

94%

Excellent

Road Tax

£195

Flat rate/year

Insurance

Grp 30-42

2625cc Petrol

Great Choice

94% pass rate, £2042/year to run. 12 points above average.

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Petrol2625cc8 years old6,518 tests75k miles avg

Annual Running Costs

Fuel (Petrol, 2625cc)

~30 mpg

£1,592

Road Tax

Flat rate (post-2017)

£195

MOT Test

£55

Predicted Repairs

Low estimate due to excellent reliability

£200

Total per year£2,042

Per month£170/mo

Per week£39/wk

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

94% MOT pass rate(Excellent)

0%National avg: 82%100%

Excellent reliability. Very few MOT failures. That's 12 points above the national average of 82%. It also outperforms the MERCEDES brand average of 87%.

At 8 years old, 94% of MERCEDES S-CLASSs from 2018 passed their MOT first time in 2026. That's based on 6,518 tests across the UK. The average mileage at this age is 75,456 miles.

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How Does It Compare?

Rank among 2018 cars128th of 649(top 20%)

Rank among MERCEDES models279th of 1,408(top 20%)

vs national average+12%(82% avg)

vs 2018 cars average+5%(89% avg)

vs MERCEDES average+7%(87% avg)

Mileage Analysis

75,456

Average miles

59,200

Expected for age

The average 2018 MERCEDES S-CLASS has 75,456 miles on the clock, which is above the expected 59,200 miles for a 8-year-old car. Higher-mileage cars often have more motorway miles, which is generally less harmful than stop-start urban driving.

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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 2018 sits between the two at 94%.

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

BMW 5 SERIES

2018 · 2998cc Petrol

£2,037/year

91%

-3%

LAND ROVER RANGE ROVER SPORT

2018 · 2995cc Petrol

£2,037/year

93%

-1%

BMW X3

2019 · 2998cc Petrol

£2,037/year

92%

-2%

MERCEDES GLC

2019 · 2996cc Petrol

£2,037/year

93%

-1%

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About the 2018 MERCEDES S-CLASS

The 2018 MERCEDES S-CLASS is a large car with a 2625cc petrol engine. 6,518 of these vehicles were MOT tested in 2026, making it a reasonably common sight on UK roads. It ranks in the top 20% of all 2018 cars for reliability.

With an average of 75,456 miles at 8 years old, MERCEDES S-CLASS owners cover more miles than the average driver.

2018 MERCEDES S-CLASS Fuel Costs

The 2625cc 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 2018 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 94% 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 2018 MERCEDES S-CLASS

At 8 years old, this is a solid used buy if you find one with good service history. Depreciation has levelled off, so you won't lose much more value. Focus on condition over mileage. If you're flexible on year, the 2020 model has the highest pass rate at 95%. With 6,518 MOT tests in our data, there's strong statistical confidence in these figures.

Common Issues to Watch For

Based on the 2018 MERCEDES S-CLASS's fuel type, age, and engine size, these are the most likely problem areas to check.

Timing Chain / Belt

Watch out

At 8 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.

Suspension Wear

Medium risk

Shock absorbers, springs, and anti-roll bar links typically need attention around this age. Listen for clunks over bumps and check for uneven tyre wear.

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 2018 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(2018)	94%	£1592	£195	Grp 30-42	£2042
BMW 5 SERIES(2018)	91%	£1592	£190	Grp 30-42	£2037-£5
LAND ROVER RANGE ROVER SPORT(2018)	93%	£1592	£190	Grp 30-42	£2037-£5
BMW X3(2019)	92%	£1592	£190	Grp 30-42	£2037-£5
MERCEDES GLC(2019)	93%	£1592	£190	Grp 30-42	£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.