Hyundai Sonata vs Kia K5: fuel economy and fuel cost
In model year 2026 the Hyundai Sonata is the cheaper of the two to fuel: about $1,290 a year for its lowest-cost configuration (Sonata Hybrid Blue, 51 MPG combined), against $2,190 for the Kia K5 (K5 w/Stop-Start, 30 MPG combined). That is $900 a year, or $4,500 over five years.
Both come from the same maker or parent group. Costs assume 15,000 miles a year and the same fuel and electricity prices for both vehicles, using the EPA combined rating (55% city, 45% highway). Each figure is rounded to $10 and every difference is calculated from the rounded values.
The EPA is still publishing model year 2027 ratings, so this page compares model year 2026, the latest complete year.
- Hybrid
- Large cars
Hyundai Sonata
Lowest fuel cost configuration
Sonata Hybrid Blue
$8.60 per 100 miles
15,000 mi/yr, same fuel prices
6 configurations in MY2026
- Gas
- Large cars
Kia K5
Lowest fuel cost configuration
K5 w/Stop-Start
$14.60 per 100 miles
15,000 mi/yr, same fuel prices
4 configurations in MY2026
What the fuel costs
Annual fuel cost of the lowest-cost configuration
- Hyundai Sonata$1,290 a year · $8.60 per 100 mi
- Kia K5$2,190 a year · $14.60 per 100 mi
Difference per year
$900
Hyundai Sonata costs less to fuel
Over 5 years
$4,500
$900 a year × 5, 15,000 mi/yr, same fuel prices
Head to head, MY2026
| Measure | Hyundai Sonata | Kia K5 |
|---|---|---|
| Lowest-cost configuration | Sonata Hybrid Blue | K5 w/Stop-Start |
| Powertrain | Hybrid | Gas |
| Combined rating | 51 MPG (better) | 30 MPG |
| City rating | 47 MPG (better) | 26 MPG |
| Highway rating | 56 MPG (better) | 37 MPG |
| Annual fuel cost | $1,290/yr (better) | $2,190/yr |
| Cost per 100 miles | $8.60 (better) | $14.60 |
| Annual cost range, all configurations | $1,290–$2,450 | $2,190–$2,440 |
| Configurations in MY2026 | 6 | 4 |
| EPA class | Large cars | Large cars |
Best configuration by powertrain
| Powertrain | Hyundai Sonata | Kia K5 |
|---|---|---|
| Gas | 32 MPG · $2,060/yr Sonata w/Stop-Start | 30 MPG · $2,190/yr K5 w/Stop-Start |
| Hybrid | 51 MPG · $1,290/yr Sonata Hybrid Blue | Not offered in MY2026 |
Each cell shows the combined rating and the annual fuel cost of the lowest-cost configuration with that powertrain.
Where each one comes out ahead
Generated from the numbers above, comparing the lowest fuel cost configurations. No subjective judgements.
Hyundai Sonata
- Lower annual fuel cost: $1,290 vs $2,190
- Higher combined rating: 51 MPG vs 30 MPG
- Higher city rating: 47 MPG vs 26 MPG
- Higher highway rating: 56 MPG vs 37 MPG
- Lower annual cost for the best gas configuration: $2,060 vs $2,190
- Offers hybrid configurations in MY2026; the Kia K5 does not
Kia K5
Not ahead on any measure listed here.
Year by year
| Model year | Hyundai Sonata | Kia K5 | ||
|---|---|---|---|---|
| Combined | Per year | Combined | Per year | |
| 2026 | 27–51 MPG | $1,290–$2,450 | 27–30 MPG | $2,190–$2,440 |
| 2025 | 27–47 MPG | $1,380–$2,450 | 27–30 MPG | $2,190–$2,440 |
| 2024 | 27–47 MPG | $1,380–$2,450 | 27–31 MPG | $2,140–$2,430 |
| 2023 | 27–52 MPG | $1,260–$2,440 | 27–31 MPG | $2,140–$2,430 |
| 2022 | 27–52 MPG | $1,260–$2,440 | 27–32 MPG | $2,040–$2,430 |
| 2021 | 27–52 MPG | $1,260–$2,440 | 27–32 MPG | $2,040–$2,430 |
Earlier model years are costed with today's fuel prices, so the table shows how each model's efficiency changed, not what fuel cost at the time. Ranges cover every configuration of that model year.
Frequently asked questions
Which is cheaper to fuel, the Hyundai Sonata or the Kia K5?
The Hyundai Sonata is cheaper: about $1,290 a year against $2,190 for the Kia K5, a difference of $900 a year. That compares the lowest-cost configuration of each in model year 2026 at 15,000 miles a year with the same fuel prices.
How much would the Hyundai Sonata save over five years?
About $4,500 ($900 a year for five years), assuming 15,000 miles a year and the same fuel prices. Your total depends on how much you drive and on local prices; see fuel cost by state.
Which has the better fuel economy rating, the Hyundai Sonata or the Kia K5?
The Hyundai Sonata is rated 51 MPG combined against 30 MPG for the Kia K5. City: 47 MPG vs 26 MPG. Highway: 56 MPG vs 37 MPG. These are the EPA ratings of each model's lowest-cost configuration.
How is the annual fuel cost calculated?
Distance of 15,000 miles a year at the EPA combined rating (55% city, 45% highway). Gasoline is priced at $4.36/gal (EIA U.S. average for regular, Sep 2026) and electricity at 18.3¢/kWh (EIA U.S. residential average, Jul 2026); premium and diesel configurations use their own EIA prices. Each result is rounded to $10, and differences are calculated from the rounded figures.
Are the Hyundai Sonata and the Kia K5 in the same class?
Yes. The EPA classes both as Large cars.