⚠️ Mercedes-Benz manufacturer position
WIS tank module access from load floor; full tank support may be needed on X167. Misfuel misuse.
Vehicle information
| Make | Mercedes-Benz |
|---|---|
| Model | GLS |
| Market status | Sold new in Great Britain — X167 (2020–present) |
| Body styles | Full-size luxury SUV |
| Generations | X166, X167 |
| Engine options | Petrol: 3.0 L inline-six petrol (M256) on UK GLS 450 Diesel: 3.0 OM656 diesel on UK GLS diesel |
| Fuel tank capacity | Approximately 90 litres |
| Fuel system | Turbo petrol M256; OM656 common-rail diesel |
| Access method | Third-row load floor access typical on UK GLS |
| Anti-siphon | Yes |
| Service portal | Mercedes-Benz WIS / XENTRY Workshop (authorised dealers) |
Misfuel risk High
Diesel variants use common-rail injection at very high pressure; petrol in diesel destroys pump lubrication and can contaminate the entire fuel circuit within seconds of running.
If the engine was not started
Drain large-capacity tank completely, new filter, prime.
If the engine was started
Petrol in OM656 diesel: major component risk if driven.
Access procedure
- Disconnect the negative battery terminal and relieve fuel system pressure per OEM procedure.
- Access the in-tank fuel pump module via the manufacturer-specified route (access panel or tank lowering).
- Drain contaminated fuel using approved recovery equipment into suitable containers for hazardous waste duty of care.
- Inspect the tank, sender unit, and lines; replace the fuel filter and any contaminated flexible lines as required.
- Reassemble, refill with the correct fuel grade, prime the low-pressure circuit, and check for leaks before start.
- If the engine was run on wrong fuel, follow OEM guidance for high-pressure pump, rail, and injector inspection before restart.
Related models
Frequently asked questions
What should I do if I put petrol in my Mercedes-Benz GLS diesel?
Do not start the engine. Arrange OEM-method tank fuel extraction and hazardous waste disposal under UK duty of care. A GBIFDA-certified technician can document the procedure for insurers.
Does Mercedes-Benz warranty cover misfuel on a GLS?
Manufacturer warranties typically exclude wrong fuel as misuse. Expect out-of-pocket or insurance-funded repair.
Can I siphon fuel from a Mercedes-Benz GLS?
UK Mercedes-Benz models usually have anti-siphon filler necks; OEM information specifies pump-module or tank removal instead.
When are injectors replaced after misfuel on a GLS?
If the engine ran on contaminated diesel, injectors and HP pump are inspected or replaced per Mercedes-Benz diagnostics; not always required if caught before start.
Need professional misfuel recovery?
Find a certified operator or read consumer guidance for your next steps.
Find an operator Consumer guidance