What is the firing order?
1-3-4-2 for both engines.
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In-depth guide
2021 Hyundai Sonata
2021 Sonata firing sequence is 1-3-4-2 on both engines. The G2.5 chart says replace plugs every 96,000 miles. No gap is printed.
| Item | Figure |
|---|---|
| Firing sequence | 1-3-4-2 on both the G1.6 T-GDi and the G2.5 GDi. |
| G2.5 interval | Replace every 96,000 miles. No kilometer figure on that line. |
| G1.6 interval | Replace marks are on the chart. Mile columns were not locked from the text layer. |
| What is not printed | No gap and no torque. |
Source: owner's manual / last verified 2026-10-16 (2021 Hyundai Sonata owner's manual, engine specification and maintenance (opens in a new tab)).
Difficulty, time, and cost are estimates when this guide gives them. Torque is a cited figure, or it is left off.
Main source: 2021 Hyundai Sonata owner's manual, engine specification and maintenance (opens in a new tab), Hyundai Motor America, published 2020-08-20, read 2026-10-16.
Spark-plug socket
A size is not printed.
| Item | Figure | Where it comes from |
|---|---|---|
| Firing sequence | 1-3-4-2 on both the G1.6 T-GDi and the G2.5 GDi. | Engine specification |
| G2.5 interval | Replace every 96,000 miles. No kilometer figure on that line. | Normal maintenance schedule, G2.5 |
| G1.6 interval | Replace marks are on the chart. Mile columns were not locked from the text layer. | Normal maintenance schedule, G1.6 |
| What is not printed | No gap and no torque. | Engine specification |
Smartstream G1.6 T-GDi
Smartstream G2.5 GDi
Firing sequence from the 2021 Sonata engine specification. Sequence only.
Illustration, not to scale; confirm with your owner's manual. This is the firing sequence only. It does not show where each cylinder sits on the engine.
Source for this drawing: 2021 Sonata owner's manual, engine specification.
1-3-4-2 for both engines.
Every 96,000 miles. No kilometer figure is on that line.
Replace marks are there. This page does not name the miles.
None is printed.
2021 Sonata Owner's Manual. The PDF title is 2021 Sonata Owners Manual and the file was created August 20, 2020. The drive belt has its own interval: drive belt.
Outbound links only. BaySheet does not sell parts. Confirm fitment on the retailer page. Amazon links are searches for a real part name plus this vehicle. Tool rows do not get a product search. The search is not a part number.
Part
Spark plugs for a 2021 Hyundai Sonata
No part number or gap is printed. G2.5 interval is every 96,000 miles. G1.6 miles stay on the chart.
2021 Sonata spark plugs (opens in a new tab)Search Amazon.com (affiliate link) (opens in a new tab)As an Amazon Associate I earn from qualifying purchases.
Tool
Spark-plug socket
A size is not printed.
1-3-4-2 for both engines.
Every 96,000 miles on the normal chart. No kilometer figure is printed on that line.
The maintenance checklist is on the site now. The email list is not sending yet, so this box will not store an address.
These guides cover the same kind of work. Their numbers belong to those vehicles, not to this one.
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