Mercedes GLS (2018)

Estimated running costs and MOT pass rates from 1,328 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

2987cc Diesel

Great Choice

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

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Diesel2987cc8 years old1,328 tests55k miles avg

Annual Running Costs

Fuel (Diesel, 2987cc)

~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 GLSs from 2018 ended in a pass in 2024, when they were about 6 years old. That's based on 1,328 tests across the UK, retests included. The average mileage recorded at those tests was 55,325 miles.

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How Does It Compare?

Rank among 2018 models327th of 607(bottom half)

Rank among Mercedes models621st of 1,376(top half)

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

vs 2018 models average+1%(89% avg)

vs Mercedes average+3%(87% avg)

Mileage Analysis

55,325

Average miles

44,400

Expected for age

The average 2018 Mercedes GLS had 55,325 miles on the clock at its 2024 MOT, which is above the expected 44,400 miles for a 6-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?

Of the years with at least 100 tests, the 2016 model has the highest MOT pass rate at 93%, while the 2018 model has the lowest at 90%. Consider a different year if reliability is a priority. Newer cars usually pass more often simply because they are younger, so compare years of a similar age.

Mercedes GLS by Year

Year	Pass Rate	Tests	Avg Mileage
2019	92%	861	48,209 mi
2018	90%	1,328	55,325 mi
2017	92%	1,425	62,721 mi
2016	93%	983	72,875 mi

Similar Cars to Consider

Mercedes E

2019 · 2925cc Diesel

£2,131/year

90%

same

Mercedes GLC

2018 · 2987cc Diesel

£2,131/year

91%

+1%

Audi A5

2017 · 2967cc Diesel

£2,281/year

89%

-1%

Ford Ranger

2019 · 3198cc Diesel

£2,281/year

87%

-3%

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About the 2018 Mercedes GLS

The 2018 Mercedes GLS is a premium performance car. Our records list a 2987cc diesel engine, though engines vary between versions. 1,328 MOT tests were recorded on this model in 2024, making it a reasonably common sight on UK roads. Among all models from 2018, the average MOT pass rate is 89%, and this model beats that benchmark.

With an average of 55,325 miles recorded at its 2024 MOT tests, Mercedes GLS owners cover more miles than the average driver.

2018 Mercedes GLS Fuel Costs

The 2987cc 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 2018 Mercedes GLS?

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 GLS Reliability Trend

The Mercedes GLS has maintained consistent MOT pass rates across model years, varying by only 2 percentage points.

Buying a Used 2018 Mercedes GLS

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.

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

Watch out

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

Watch out

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

Dual Mass Flywheel

Watch out

Larger diesel engines put extra strain on the dual mass flywheel. Listen for rattling at idle. Replacement with clutch is £800-£1,500.

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 GLS 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 GLS(2018)	90%	£1,676	£200	Grp 30-42	£2,131
Mercedes E(2019)	90%	£1,676	£200	Grp 30-42	£2,131same
Mercedes GLC(2018)	91%	£1,676	£200	Grp 30-42	£2,131same
Audi A5(2017)	89%	£1,676	£200	Grp 30-42	£2,281+£150
Ford Ranger(2019)	87%	£1,676	£200	Grp 35-50	£2,281+£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 2018 Mercedes GLS

Is the 2018 Mercedes GLS reliable?

Excellent reliability. Very few MOT failures. 90% of MOT tests on 2018 Mercedes GLSs ended in a pass, from 1,328 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 2018 Mercedes GLS 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 2018 Mercedes GLS?

90% of 1,328 MOT tests on the 2018 Mercedes GLS ended in a pass (DVSA MOT data for tests in 2024, retests included). That ranks it 327th of 607 models first registered in 2018 (bottom half).

Which year Mercedes GLS has the best MOT pass rate?

Of the years with at least 100 tests, the 2016 Mercedes GLS has the highest MOT pass rate at 93% and the 2018 the lowest at 90%. Newer cars usually pass more often simply because they are younger and have done fewer miles.

What is the average mileage for a 2018 Mercedes GLS?

The average mileage recorded at MOT tests on the 2018 Mercedes GLS is 55,325 miles, which is above the expected 44,400 miles for a 6-year-old car. Higher-mileage cars often have more motorway miles, which is generally less harmful than stop-start urban driving.