MERCEDES M8 (2018)
Running costs, reliability data, and common problems from 111 real MOT tests.
Annual Cost
£1,995
£166/month
MOT Pass Rate
79%
Average
Road Tax
£195
Flat rate/year
Insurance
Grp 25-38
2143cc Diesel
Check Carefully
79% pass rate, £1995/year to run. Close to the national average.
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Annual Running Costs
~40 mpg
Flat rate (post-2017)
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
Average reliability. Expect some repairs as it ages. That's close to the national average of 82%. It falls below the MERCEDES brand average of 87%.
At 8 years old, 79% of MERCEDES M8s from 2018 passed their MOT first time in 2026. That's based on 111 tests across the UK. The average mileage at this age is 198,084 miles.
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How Does It Compare?
Mileage Analysis
198,084
Average miles
59,200
Expected for age
The average 2018 MERCEDES M8 has 198,084 miles on the clock, which is well above the expected 59,200 miles for a 8-year-old car. Check service history carefully, as high-mileage cars need consistent maintenance to stay reliable.
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Best Year to Buy?
The most reliable year is the 2019 model with a 82% MOT pass rate, while the 2017 model has the lowest at 76%. The 2018 sits between the two at 79%.
MERCEDES M8 by Year
Similar Cars to Consider
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About the 2018 MERCEDES M8
The 2018 MERCEDES M8 is a family car with a 2143cc diesel engine. 111 of these vehicles were MOT tested in 2026, making it a rare model on UK roads. It sits in the bottom 96% of 2018 cars for MOT pass rates.
With an average of 198,084 miles at 8 years old, MERCEDES M8 owners cover more miles than the average driver. High-mileage examples should be checked carefully for wear on suspension, brakes, and drivetrain components.
2018 MERCEDES M8 Fuel Costs
The 2143cc diesel engine offers a reasonable balance between performance and economy. Expect around 40 mpg in mixed driving, which works out to roughly £1,245 per year at current diesel prices of 148p per litre (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 M8?
Total estimated annual running cost is £1,995 (£166/month), broken down as £1245 fuel, £195 road tax, £55 MOT, and £500 predicted repairs. Repair costs are moderate, reflecting the 79% pass rate. Keeping on top of servicing will help avoid surprises.
MERCEDES M8 Reliability Trend
Newer MERCEDES M8s show better MOT pass rates than older ones, with an average improvement of 5 percentage points.
Buying a Used 2018 MERCEDES M8
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 82%.
Common Issues to Watch For
Based on the 2018 MERCEDES M8's fuel type, age, and engine size, these are the most likely problem areas to check.
DPF (Diesel Particulate Filter)
Watch outShort journeys clog the DPF. Replacement costs £1,000-£2,500. Check the DPF warning light and ask about driving patterns.
Turbo Wear
Watch outDiesel turbos work harder and wear faster. Listen for whining noises and check for oil leaks around the turbo housing.
AdBlue System
Medium riskPost-2015 diesels use AdBlue for emissions. Sensor failures and tank heater issues are common. Budget £200-£500 for repairs.
EGR Valve
Watch outExhaust Gas Recirculation valves clog with carbon deposits, causing rough running and poor economy. Cleaning costs £150-£300, replacement £300-£600.
Dual Mass Flywheel
Watch outLarger 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 riskShock absorbers, springs, and anti-roll bar links typically need attention around this age. Listen for clunks over bumps and check for uneven tyre wear.
Clutch Wear
Watch outWith an average of 198k 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 riskHigh-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 riskWorn 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 riskAlways 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 M8 stacks up against similar cars for annual running costs, insurance, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Insurance | Total/yr |
|---|---|---|---|---|---|
| MERCEDES M8(2018) | 79% | £1245 | £195 | Grp 25-38 | £1995 |
| VOLKSWAGEN GOLF(2018) | 92% | £1037 | £190 | Grp 18-32 | £1482-£513 |
| FORD TRANSIT(2017) | 81% | £1037 | £190 | Grp 18-32 | £1632-£363 |
| FORD KUGA(2019) | 91% | £1037 | £190 | Grp 18-32 | £1482-£513 |
| KIA SPORTAGE(2016) | 85% | £1037 | £135 | Grp 18-32 | £1577-£418 |
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.
Related Mercedes Models
Explore other Mercedes cars or similar models in the same category.
MERCEDES A
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MERCEDES C
2017 · 1991cc Hybrid
MERCEDES A-CLASS
2017 · 1461cc Diesel
VOLKSWAGEN GOLF
2018 · 1968cc Diesel
FORD TRANSIT
2017 · 1995cc Diesel
FORD KUGA
2019 · 1997cc Diesel
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