When to replace spark plugs and glow plugs in the Lexus IS
Lexus IS
Lexus IS•
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There is no single plug replacement interval for every Lexus IS. The regional manual reviewed here specifies 60,000 km for the IS 300 with the 8AR-FTS 2.0-litre turbo engine and 100,000 km for the IS 350 with the 2GR-FKS V6. Apply these figures only to the corresponding vehicle specifications.
The hybrid IS 300h also needs spark plugs. Diesel IS 200d and IS 220d models use a different system: glow plugs help establish conditions for fuel ignition. Their maintenance cannot be planned using a petrol IS schedule.
This guide covers engine differences, fault symptoms and parts selection. Before ordering plugs, confirm the VIN, model year and the vehicle’s service documentation.
Identifying the correct type of plug
Start with the engine rather than the badge on the boot lid. The IS 300 name has been used for different powertrains. In this article, the 60,000 km interval applies specifically to the four-cylinder 8AR-FTS turbo engine in the cited manual.
Page 665 of the IS 300 and IS 350 manual lists the engine codes 8AR-FTS and 2GR-FKS. These identifiers connect the maintenance schedule to the actual vehicle and help avoid buying plugs that look similar but do not fit the specification.
| Version | Powertrain | Plug type |
|---|---|---|
| IS 300 in the manual | 8AR-FTS, 2.0-litre turbo | 4 spark plugs |
| IS 350 in the manual | 2GR-FKS, 3.5-litre V6 | 6 spark plugs |
| IS 300h | 2.5-litre petrol hybrid | 4 spark plugs |
| IS 200d / IS 220d | 2.2-litre diesel | Glow plugs |
| Other IS versions | Identify by VIN | Their own catalogue and schedule |
Why a hybrid needs spark plugs
The IS 300h technical description on newsroom.lexus.eu specifies a four-cylinder 2.5-litre petrol engine. Its mixture is ignited by a spark when the engine runs, so the electrical part of the powertrain does not eliminate plug replacement.
Check the IS 300h interval in its own documentation. Do not subtract electric driving from the odometer reading or transfer the IS 300 turbo interval to the hybrid because their names are similar.
The IS 250, earlier IS 200 and IS 300, and other configurations need separate parts checks. For a vehicle imported into the UAE, take its original specification and service history into account.
Spark plug replacement mileage
Page 526 of the regional manual places the IS 300 replacement mark at 60,000 km and explicitly specifies 100,000 km for the IS 350. The plug entries set no separate limit in months. If your vehicle’s service book includes a time limit, follow it.
| Engine covered | Scheduled replacement | Scope |
|---|---|---|
| IS 300, 8AR-FTS | 60,000 km | Not every IS 300 |
| IS 350, 2GR-FKS | 100,000 km | Match year and specification |
| Other petrol IS and IS 300h | Their own schedules | Do not transfer the interval automatically |
Heat and traffic do not give one universal adjustment
During extended idling with the air conditioning running, the engine operates even when mileage barely increases. Explain this use to the workshop and check additional maintenance requirements. Do not arbitrarily halve the plug interval solely because of the climate.
When earlier diagnosis is needed
Hesitation under load, an unstable idle and difficult starting need investigation regardless of mileage. Plugs, coils, injectors or mechanical faults may be responsible. A misfire code alone does not establish that a plug is defective.
The troubleshooting article on ngkntk.com explains how carbon, fuel and oil on a plug’s firing end can disrupt ignition. If the source of fouling remains, a new set may resolve the rough running only temporarily.
If the engine shakes severely and the malfunction indicator flashes, stop accelerating and pull over safely. Severe misfires can damage the catalytic converter; arrange transport to a workshop if the engine continues running roughly.
Glow plugs in the IS 200d and IS 220d
The archived Lexus range description confirms that the IS 200d replaced the IS 220d and used a 2.2-litre diesel engine. These versions matter when servicing a used IS, even where most available cars have petrol engines.
A glow plug heats the area inside a cylinder to support diesel starting and stable operation after start-up. It does not generate a spark and cannot be replaced by a spark plug. Engine specification, heating element type and electrical characteristics all matter when selecting the part.
When to check and replace them
The petrol manual’s 60,000 and 100,000 km intervals do not apply to diesel glow plugs. No single interval for all IS 200d and IS 220d models is established here. Follow your version’s documentation and diagnose starting complaints before replacing parts.
The article on denso-am.eu lists difficult starting, uneven running and smoke among possible fault symptoms. It also advises checking the electrical supply and control system for the underlying cause: a faulty relay or controller can damage new plugs.
The technician checks fault codes, wiring, glow control and the plugs using a suitable test method. Similar complaints may involve the battery, starter, injectors or compression. A lack of freezing weather does not make the glow system unnecessary.
Why removal needs care
The NGK technical guide advises against testing a glow plug by applying battery voltage until it glows red, as this can damage the heater. It also highlights the care needed when removing and installing ceramic plugs.
Do not force out a seized plug. Use repair documentation for the removal procedure, force limits and installation torque. Decide whether to replace one plug or a set after checking the others and correcting the cause of failure.
Choosing plugs and preparing for replacement
Page 670 of the IS 300 and IS 350 manual gives the following plug designations and nominal gaps. It requires iridium-tipped plugs and prohibits adjusting their gaps.
| Version covered | Designation | Gap |
|---|---|---|
| IS 300, 8AR-FTS | NGK DILFR7K9G | 0.9 mm |
| IS 350, 2GR-FKS | DENSO FK20HBR8 | 0.8 mm |
This table does not cover the IS 300h, diesels or other engines. Check the part number against the VIN and current catalogue, including any superseding numbers. Matching thread size or appearance alone does not establish compatibility.
Petrol engine replacement checklist
☐ Confirm the engine, plug quantity and catalogue number.
☐ Switch the ignition off; confirm READY is off on a hybrid.
☐ Let the engine cool and clean the plug wells.
☐ Inspect coils, boots and electrical connectors.
☐ Check required disassembly and any seals needed.
☐ Prepare the correct socket and tightening specifications.
The guide on ngksparkplugs.com explains why both insufficient and excessive tightening are harmful. Start each plug without cross-threading, then tighten to the engine and component specification. One torque value cannot cover every Lexus IS.
Do not bend the electrode of an unsuitable plug or lubricate its threads without explicit manufacturer instructions. Keep removed plugs in cylinder order so their condition can be compared with diagnostic findings.
Frequently asked questions about Lexus IS plugs
Should coils be replaced with the plugs
Working coils do not automatically need replacement with each set of plugs. For rough running, check the coil, boot, power supply and connector. Oil in a plug well calls for finding the leak, otherwise new parts will face the same conditions.
What if the service history is unknown
When browsing current offers for the Lexus IS, request invoices showing the mileage and designation of the installed plugs. A general major-service entry does not confirm that the ignition or glow system was actually serviced.
If records are unavailable, identify the correct schedule and agree on inspection with the workshop based on mileage and engine condition. After replacement, retain the date, mileage and part numbers. For a diesel, also keep the glow system test results.
Can cleaning extend service life
Cleaning cannot restore worn electrodes or cracked ceramic. Repeated fouling needs its cause investigated, and appearance alone does not cancel scheduled replacement. Do not apply petrol spark plug testing or cleaning methods to glow plugs.
Why is the engine running poorly after replacement
Check parts suitability, connector and boot seating, insulator condition and installation quality. Do not assume that new plugs need a running-in period. If the engine runs unevenly, return to diagnosis.
Conclusion
For the Lexus IS, identify the engine and plug type first. The IS 300 turbo and IS 350 discussed here have different intervals, the IS 300h needs its own schedule, and diesel IS 200d and IS 220d models need glow system maintenance. VIN-based parts selection and recorded service history help prevent mistakes at the next service.
