Is the 2018 MERCEDES SL reliable?

Excellent reliability. Very few MOT failures. 93% of MERCEDES SLs from 2018 passed their MOT first time in 2026, based on 1,022 tests. That's 11 points above the national average of 82%.

How much does a 2018 MERCEDES SL 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 SL?

The 2018 MERCEDES SL has a 93% MOT pass rate based on 1,022 tests in 2026. This ranks 187 out of 649 cars from 2018.

Which year MERCEDES SL is most reliable?

The 2019 MERCEDES SL has the highest MOT pass rate at 97%. The least reliable year is 1990 at 81%.

MERCEDES SL (2018)

Q: What is the average mileage for a 2018 MERCEDES SL?

The average mileage for a 2018 MERCEDES SL is 25,750 miles, which is significantly below the expected 59,200 miles for a 8-year-old car. Low-mileage examples may have spent time sitting unused, so check for issues like corroded brakes or perished rubber seals.

Running costs, reliability data, and common problems from 1,022 real MOT tests.

Annual Cost

£2,042

£170/month

MOT Pass Rate

93%

Excellent

Road Tax

£195

Flat rate/year

Insurance

Grp 35-50

4663cc Petrol

Great Choice

93% pass rate, £2042/year to run. 11 points above average.

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Petrol4663cc8 years old1,022 tests26k miles avg

Annual Running Costs

Fuel (Petrol, 4663cc)

~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

93% MOT pass rate(Excellent)

0%National avg: 82%100%

Excellent reliability. Very few MOT failures. That's 11 points above the national average of 82%. It also outperforms the MERCEDES brand average of 87%.

At 8 years old, 93% of MERCEDES SLs from 2018 passed their MOT first time in 2026. That's based on 1,022 tests across the UK. The average mileage at this age is 25,750 miles.

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How Does It Compare?

Rank among 2018 cars187th of 649(top 29%)

Rank among MERCEDES models383th of 1,408(top 27%)

vs national average+11%(82% avg)

vs 2018 cars average+4%(89% avg)

vs MERCEDES average+6%(87% avg)

Mileage Analysis

25,750

Average miles

59,200

Expected for age

The average 2018 MERCEDES SL has 25,750 miles on the clock, which is significantly below the expected 59,200 miles for a 8-year-old car. Low-mileage examples may have spent time sitting unused, so check for issues like corroded brakes or perished rubber seals.

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Best Year to Buy?

The most reliable year is the 2019 model with a 97% MOT pass rate, while the 1990 model has the lowest at 81%. The 2018 sits between the two at 93%.

MERCEDES SL by Year

Year	Pass Rate	Tests	Avg Mileage
2019	97%	851	19,987 mi
2018	93%	1,022	25,750 mi
2017	94%	1,847	30,630 mi
2016	95%	2,240	36,109 mi
2015	92%	2,222	40,591 mi
2014	92%	2,892	47,357 mi
2013	89%	2,796	49,450 mi
2012	90%	1,136	50,476 mi
2011	92%	579	50,602 mi
2010	88%	955	62,402 mi
2009	87%	1,222	63,020 mi
2008	90%	1,940	65,610 mi
2007	88%	1,792	71,215 mi
2006	87%	1,832	73,640 mi
2005	88%	2,430	75,394 mi
2004	88%	4,036	77,676 mi
2003	86%	5,173	75,808 mi
2002	88%	2,083	74,421 mi
2001	90%	528	78,534 mi
2000	86%	955	84,195 mi
1999	87%	1,617	84,924 mi
1998	86%	2,018	89,595 mi
1997	87%	2,117	93,418 mi
1996	88%	1,778	93,971 mi
1995	85%	1,627	99,248 mi
1994	88%	1,244	93,271 mi
1993	88%	462	85,167 mi
1992	87%	312	90,571 mi
1991	86%	288	78,703 mi
1990	81%	186	88,429 mi

Similar Cars to Consider

LAND ROVER RANGE ROVER

2017 · 4999cc Petrol

£2,037/year

91%

-2%

JAGUAR F-TYPE

2017 · 5000cc Petrol

£2,037/year

94%

+1%

BMW X6

2017 · 4395cc Petrol

£2,037/year

92%

-1%

BMW M5

2016 · 4395cc Petrol

£2,097/year

94%

+1%

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About the 2018 MERCEDES SL

The 2018 MERCEDES SL is a performance with a 4663cc petrol engine. 1,022 of these vehicles were MOT tested in 2026, making it a reasonably common sight on UK roads. Among all cars from 2018, the average MOT pass rate is 89%, and this model beats that benchmark.

With an average of 25,750 miles at 8 years old, MERCEDES SL owners tend to use this car less than the typical driver. Very low mileage could mean the car has been garaged or used only for short trips, which can cause its own issues like battery drain and moisture buildup.

2018 MERCEDES SL Fuel Costs

The 4663cc 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 SL?

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 93% pass rate. These cars rarely fail their MOT, so unexpected bills are less likely.

MERCEDES SL Reliability Trend

Newer MERCEDES SLs show better MOT pass rates than older ones, with an average improvement of 4 percentage points.

Buying a Used 2018 MERCEDES SL

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 2019 model has the highest pass rate at 97%.

Common Issues to Watch For

Based on the 2018 MERCEDES SL'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 SL stacks up against similar cars for annual running costs, insurance, and tax.

Car	Pass Rate	Fuel/yr	Tax/yr	Insurance	Total/yr
MERCEDES SL(2018)	93%	£1592	£195	Grp 35-50	£2042
LAND ROVER RANGE ROVER(2017)	91%	£1592	£190	Grp 35-50	£2037-£5
JAGUAR F-TYPE(2017)	94%	£1592	£190	Grp 35-50	£2037-£5
BMW X6(2017)	92%	£1592	£190	Grp 35-50	£2037-£5
BMW M5(2016)	94%	£1592	£250	Grp 35-50	£2097+£55

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.