KIA STONIC GT-LINE S ISG MHEV (2021)
Running costs, reliability data, and common problems from 1,637 real MOT tests.
Annual Cost
£1,405
£117/month
MOT Pass Rate
97%
Excellent
Road Tax
£195
Flat rate/year
Insurance
Grp 1-8
998cc Hybrid
Great Choice
97% pass rate, £1405/year to run. 15 points above average.
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Annual Running Costs
~50 mpg
Flat rate (post-2017)
Low estimate due to excellent reliability
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
Excellent reliability. Very few MOT failures. That's 15 points above the national average of 82%. It also outperforms the KIA brand average of 86%.
At 5 years old, 97% of KIA STONIC GT-LINE S ISG MHEVs from 2021 passed their MOT first time in 2026. That's based on 1,637 tests across the UK. The average mileage at this age is 20,088 miles.
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How Does It Compare?
Mileage Analysis
20,088
Average miles
37,000
Expected for age
The average 2021 KIA STONIC GT-LINE S ISG MHEV has 20,088 miles on the clock, which is below the expected 37,000 miles for a 5-year-old car. This suggests lighter use than average, which generally means less wear on major components.
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Best Year to Buy?
The most reliable year is the 2022 model with a 100% MOT pass rate, while the 2021 model has the lowest at 97%. Consider a different year if reliability is a priority.
KIA STONIC GT-LINE S ISG MHEV by Year
Similar Cars to Consider
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About the 2021 KIA STONIC GT-LINE S ISG MHEV
The 2021 KIA STONIC GT-LINE S ISG MHEV is a city car with a 998cc hybrid engine. 1,637 of these vehicles were MOT tested in 2026, making it a reasonably common sight on UK roads. It ranks in the top 9% of all 2021 cars for reliability.
With an average of 20,088 miles at 5 years old, KIA STONIC GT-LINE S ISG MHEV owners tend to use this car less than the typical driver.
2021 KIA STONIC GT-LINE S ISG MHEV Fuel Costs
The modest 998cc hybrid engine keeps fuel costs low, which is a real advantage for a city car. Expect around 50 mpg in mixed driving, which works out to roughly £955 per year at current hybrid prices of 142p per litre (based on 7,400 miles per year). As a hybrid, real-world fuel costs will vary significantly depending on how much electric-only driving you do.
What does it cost to own a 2021 KIA STONIC GT-LINE S ISG MHEV?
Total estimated annual running cost is £1,405 (£117/month), broken down as £955 fuel, £195 road tax, £55 MOT, and £200 predicted repairs. The low repair estimate reflects the excellent 97% pass rate. These cars rarely fail their MOT, so unexpected bills are less likely.
Buying a Used 2021 KIA STONIC GT-LINE S ISG MHEV
At 5 years old, the KIA STONIC GT-LINE S ISG MHEV offers good value with plenty of life remaining. Most manufacturer warranties will have expired, so a pre-purchase inspection is worth the cost.
Common Issues to Watch For
Based on the 2021 KIA STONIC GT-LINE S ISG MHEV's fuel type, age, and engine size, these are the most likely problem areas to check.
Hybrid Battery Health
Medium riskAfter 5 years, hybrid battery capacity may have reduced. A full replacement costs £2,000-£4,000, though reconditioning is cheaper at £500-£1,500.
Inverter and Power Electronics
Low riskThe inverter converts DC to AC for the electric motor. Failures are expensive (£1,500+) but relatively rare. Listen for unusual buzzing sounds.
Regenerative Braking
Medium riskBrake discs can corrode from reduced use (the electric motor handles most braking). Surface rust is normal but deep pitting needs attention.
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 2021 KIA STONIC GT-LINE S ISG MHEV stacks up against similar cars for annual running costs, insurance, and tax.
| Car | Pass Rate | Fuel/yr | Tax/yr | Insurance | Total/yr |
|---|---|---|---|---|---|
| KIA STONIC GT-LINE S ISG MHEV(2021) | 97% | £955 | £195 | Grp 1-8 | £1405 |
| TOYOTA YARIS(2019) | 93% | £1137 | £190 | Grp 12-25 | £1582+£177 |
| VOLVO XC40(2021) | 93% | £1137 | £190 | Grp 12-25 | £1582+£177 |
| HONDA JAZZ EX I-MMD CVT(2021) | 96% | £1137 | £190 | Grp 12-25 | £1582+£177 |
| FORD PUMA TITANIUM MHEV(2021) | 95% | £955 | £190 | Grp 1-8 | £1400-£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.
Related Kia Models
Explore other Kia cars or similar models in the same category.
KIA SPORTAGE
2016 · 1700cc Diesel
KIA PICANTO
2018 · 998cc Petrol
KIA CEED
2012 · 1591cc Diesel
TOYOTA YARIS
2019 · 1497cc Hybrid
VOLVO XC40
2021 · 1470cc Hybrid
HONDA JAZZ EX I-MMD CVT
2021 · 1498cc Hybrid
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