DN8 (8th generation) · 2020–2025 · Mid-size sedan
2021 Hyundai Sonata parts and specs
Everything you need to own and maintain this exact model year. Verified specifications, part numbers, and the problems that recur, in one place.
Last verified
Quick facts
Specifications for the 2020–2025 Sonata
Oil & filter
Viscosity, capacity, filter part numbers, change interval
Battery
BCI group size, cold cranking amps, AGM or flooded
Tires & wheels
Factory sizes by trim, pressures, bolt pattern, lug torque
Wiper blades
Driver, passenger and rear blade lengths
Air & cabin filters
Cabin and engine air filter part numbers, locations, intervals
Bulbs
Headlight, fog and marker bulb types
Brakes
Rotor diameters, pad references, service notes
Fluids
Transmission fluid, coolant, brake fluid and capacities
Service schedule
What's actually due at every mileage interval
Problems & reliability
Documented failures, recalls, and which years to avoid
Oil light reset
Step-by-step maintenance light reset, no tools
Key fob battery
Which coin cell the remote takes
Specs
Towing, weight, fuel tank, fuel economy
These specifications are shared across every Sonata of the DN8 (8th generation) generation. See the 2020–2025 Hyundai Sonata overview for the full picture, or the Hyundai Sonata guide to compare every generation.
What changed for the 2021 Hyundai Sonata
- 2021N Line trim introduced with the 2.5T Smartstream engine; 1.6T dropped from most trims
Known problems with the 2021 Hyundai Sonata
2 of the 2 issues we track for the 2020–2025 generation are documented against the 2021 model year.
2.5L Smartstream (G4KN) oil dilution and oil consumption
moderateThe base 2.5L Smartstream engine has a reported pattern of unburned fuel diluting the engine oil (lowering its viscosity and lubricating ability) along with above-average oil consumption, which some independent repair shops and parts suppliers attribute to a piston-ring design issue. Owners are advised to check oil level and condition between changes rather than assume the interval is safe to stretch. No dedicated NHTSA recall covers this as of this review.
Typical cost: $0 (monitoring/top-offs) to $4,000+ for engine work if wear becomes severe
N Line oil-cap vs. owner's-manual viscosity confusion
minorThe 2.5T N Line's oil fill cap is marked 0W-20, but the owner's manual for this specific powertrain specifies 0W-30 as the factory-fill viscosity, a discrepancy widely discussed among owners and independent shops, some of whom have used the wrong oil as a result. Not a mechanical defect, but a documented source of incorrect oil-change service.
Typical cost: N/A, verify viscosity against the owner's manual, not the cap, before an oil change
Full detail, costs and sources on the Hyundai Sonata problems and years to avoid guide.
Which engines were offered in the 2021 Sonata?
| Engine | Trims | Oil | Oil capacity |
|---|---|---|---|
| 2.5L 4-cylinder (Smartstream G4KN GDI) | SE, SEL, Limited (2.5L) | 0W-20 | 6.1 qt |
| 1.6L Turbo 4-cylinder (Smartstream G1.6 T-GDI) | Limited 1.6T | 0W-20 | 5.1 qt |
| 2.5L Turbo 4-cylinder (Smartstream G2.5 T-GDI, N Line) | N Line | 0W-30 | 6.1 qt |
| 1.6L Turbo Hybrid (Smartstream G1.6 T-GDI + electric motor) | Hybrid, Hybrid Limited, Hybrid Blue | 0W-20 | 5.1 qt |
About the Hyundai Sonata
The Hyundai Sonata is the brand's midsize sedan and, for much of the 2011–2025 span covered here, a cautionary tale about engine manufacturing quality alongside genuinely good value. 0T GDI engines are the center of Hyundai's biggest-ever US recall saga: manufacturing debris left in connecting-rod oil passages caused a wave of engine seizures and fires, triggering two NHTSA recalls (15V-568, then the broader 17V-226), a Knock Sensor Detection System (KSDS) software campaign, and, after a November 2020 NHTSA consent order found Hyundai and Kia had moved too slowly and misreported data, a lifetime engine warranty extension for affected owners who install the KSDS update. The same generation's Sonata Hybrid was separately recalled (23V-651) for an ABS module that could short-circuit and start an engine-bay fire, with owners told to park outside.
0L hybrid/PHEV; Theta-family warranty coverage extends into its early years. 0L) shared with the Sonata Hybrid/Hybrid Limited. 3. Because of the recall history, checking a Sonata's VIN against NHTSA and Hyundai's recall lookup before buying or servicing one is more important here than on almost any other nameplate in this database.
For how the specifications changed across every generation, see the full Hyundai Sonata guide.
Other Hyundai Sonata years
Sources
- Wikipedia, Hyundai Smartstream engine family (G1.6T, G1.6T Hybrid, displacement/output data)
- AMSoil lookup, 2022 Sonata 2.5L oil viscosity/capacity
- Costa Oils, 2023 Sonata 2.5L Turbo (N Line) oil guide
- Hyundai Forums, N Line owner's manual 0W-30 vs. 0W-20 cap discussion
- Goodyear, 2024 Sonata factory tire fitments by trim
- Headquarter Hyundai, 2020 Sonata fuel tank capacity and EPA mpg
- US News, 2021 Sonata Limited 1.6T engine specs
- Go-Parts, 2021–2024 Hyundai/Kia 2.5L Smartstream (G4KN) oil dilution/piston-ring notes