Plan an SL350 R230 service around the exact engine, fitted equipment and dated maintenance history. The badge covers a 3.7-litre M112 and two 3.5-litre M272 applications. NGK lists 12 spark plugs for the M112 and six for the M272; the later M272 also has a different air-filter application.
Coverage: SL350 R230 with M112.973, M272.966 or M272.968, subject to the engine and source conditions below. R129, R231, SL500 and AMG versions require separate specifications.
Which SL350 engine do you have?
| SL350 R230 application | Engine / displacement | MANN output | MANN dates |
|---|---|---|---|
| 230.467 | M112.973 / 3,724 cc | 180 kW / 245 hp | 11/02–02/06 |
| 230.456 | M272.966 / 3,498 cc | 200 kW / 272 hp | 03/06–04/08 |
| 230.458 | M272.968 / 3,498 cc | 232 kW / 316 hp | 03/08–03/12 |
These are MANN catalogue identifiers. The two 3.5-litre entries have the same displacement but different engine codes and outputs. Check the actual vehicle documentation or ask the workshop to establish the engine from vehicle details, especially around a changeover or after an engine replacement.
Use the whole application when discussing parts. A kit labelled “SL350 2003–2012” can span different plug quantities and air-filter references. Its contents should match the identified work and engine.
Service A and B: record the complete reminder
The inspected 2008 manual has an ASSYST PLUS service-interval section. It describes short service A and long service B, with time or distance information and due/overdue messages. Match earlier cars to their own manual rather than assuming every edition uses identical instructions.
Give the garage the full display and mileage. Ask it to identify scheduled inspections and any additional renewals from the car’s service requirements and history. A service letter cannot establish when the plugs or individual filters were last changed.
Our general Service A and Service B guides provide background. The engine distinctions here help make the workshop quote specific to the R230.
Keep each maintenance item identifiable
| Record | What to establish |
|---|---|
| Engine oil and oil filter | Exact product, MB approval, quantity, filter reference, date and mileage. |
| Spark plugs | M112 or M272 application, full reference and quantity fitted. |
| Engine air filtration | Correct reference and complete supplied contents. |
| Cabin filter | Exact R230 application and renewal date. |
| Brake fluid | Actual renewal date, separate from checking the level. |
| Transmission | Gearbox identity and previous fluid/filter work. |
| Roof and suspension | Fitted equipment, symptoms and separate diagnostic findings. |
If records are missing, ask the workshop to distinguish scheduled work from recommendations to establish a baseline. Retain the itemised invoice and service-record update together.
Budget for the engine differences
NGK’s M112.973 entry specifies 12 PFR5G-11 plugs; its M272.966/.968 row specifies six PLKR7A plugs. Check whether a quoted parts price covers a complete set.
MANN lists C 3698/3-2 air filtration for the M112.973 and M272.966. The later M272.968 uses C 3689 with a stated requirement of two pieces. Our SL350 filters and spark-plugs guide keeps those applications separate and supplies relevant buying links.
The later M272.968 oil guide uses the 2008 manual’s 8-litre change reference and approval table. Its oil instructions are specifically scoped to that later version; earlier M112.973 and M272.966 cars need their own applicable oil guidance.
A low-mileage roadster still needs dates
The 2008 manual says the service timer does not count periods when the battery is disconnected. Record those dates and tell the workshop so elapsed time can be accounted for.
That manual specifies brake-fluid renewal every two years. Keep the actual renewal date and confirm the requirements for your own edition. A generous reminder countdown after storage is not a complete calendar history.
Identify suspension and roof work separately
Do not assume every SL350 has ABC suspension. Mercedes’ archive entry for the 230.456 M272.966 identifies coil springs and ABC as optional equipment. Confirm what is fitted before agreeing to system-specific parts or fluid work.
Provide roof, battery, suspension or gearbox symptoms with the service request, and ask the garage to identify diagnostic work separately. An engine service should not be presented as a cure for an unrelated system fault.
Ask the final quotation to show inspections, renewals, parts, labour and VAT. Resetting the reminder should follow the completed service, with the work itself recorded on the invoice.
Explore the Mercedes maintenance hub. For warning lamps, gearbox, roof or suspension investigation, see our SL R230 diagnostic scanner guide.
Sources and coverage
- Mercedes 2008 R230 manual, printed pages 193–194 / PDF pages 196–197: service messages and battery time; printed page 306 / PDF page 309: brake fluid.
- MANN 2024–26 catalogue, printed page 234 / PDF page 290: engines and filters.
- NGK UK 2024, printed page 48 / PDF page 50: plug references and quantities.
- Mercedes-Benz archive: SL350 230.456: engine and optional ABC equipment.
Checked 20 October 2026. The Mercedes-hosted manual is the April 2008 English R230 edition, whose SL350 engine table lists the later 232 kW version. Match your car’s manual, market and equipment; catalogue dates are application ranges, not UK registration cut-offs.
