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Fuels
Fuels
Choose fuel according to the requirements of the exact engine. The prescribed standard, octane rating and approved fuel composition govern.
Which fuel belongs in my vehicle?
The information is usually inside the fuel-filler flap and in the owner’s manual. A model name or the designation TSI, TFSI or TDI alone is not enough for an exact choice.
| Fuel | Standard and label | What to check |
|---|---|---|
| Unleaded petrol | EN 228, E5 or E10 | Prescribed octane rating and permitted ethanol content. |
| B7 diesel | EN 590 | Normal diesel fuel where prescribed by the manufacturer. |
| Paraffinic diesel, such as HVO100 | EN 15940, XTL | Only for vehicles whose manufacturer expressly approves its use. |
| Compressed natural gas | CNG | Only for vehicles designed and approved by the manufacturer to use CNG. |
E5, E10 and E20 mean petrol containing no more than 5%, 10% or 20% ethanol by volume. B7 means diesel containing no more than 7% FAME by volume. These labels do not state the octane or cetane number. Explaining a label does not approve the fuel for a particular vehicle. E20 is not automatically assigned to the EN 228 row above; verify suitability from the manufacturer documentation and vehicle label.
For older vehicles, verify E10 compatibility. Higher-octane petrol is not automatically E5; always check the pump label.
In plug-in hybrids driven mainly on electricity, petrol can remain in the tank for a long time. Follow the exact model manual for fuel renewal. For example, the CUPRA Terramar e-HYBRID manual, 11/2025 edition, states that every 6 months enough petrol should be used for the reserve warning to come on and the tank should then be refilled. This is a model-specific instruction, not a general rule for all hybrids or a general recommendation to drive into the reserve.
Petrol – what does the octane rating mean?
The octane rating describes petrol’s resistance to combustion knock. Europe uses the RON designation, for example 95, 98 or 100.
Examples of vehicle label information
| Vehicle information | How to read it |
|---|---|
| 95 / min. 91 RON | 95 petrol is recommended; the manufacturer permits at least 91 under the conditions in the manual. |
| min. 95 RON | Use petrol with an octane rating of at least 95. |
| 98 / min. 95 RON | 98 petrol is recommended; 95 is also permitted, possibly with a slight reduction in performance. |
A recommended value and a permitted minimum are not the same. Emergency use of lower-octane fuel is governed solely by the exact vehicle manual.
98 or 100 petrol can benefit engines able to use its properties. A higher octane rating alone does not guarantee more power or lower consumption in every vehicle.
Diesel – what does the cetane number mean?
The cetane number describes diesel fuel’s ability to ignite after injection into hot compressed air. A higher value generally means a shorter ignition delay and can benefit cold starting and combustion noise.
Diesel meeting EN 590 has a minimum cetane number of 51. It is not the only quality measure; cleanliness, lubricity and low-temperature properties also matter.
Why avoid regularly driving into the reserve?
We recommend refuelling in good time, ideally before the reserve warning comes on.
- DPF regeneration
- Depending on the vehicle, a low fuel level can restrict or interrupt regeneration. If both the DPF and reserve warnings are on, refuel before attempting the prescribed regeneration drive.
- Fuel-operated auxiliary heater
- At a low fuel level it may not start or may switch off early. This need not indicate a heater fault. The vehicle manual defines the exact conditions.
Do not run the tank completely dry. Fuel exhaustion can cause irregular running or stop the engine.
Do fuel additives make sense?
Suitable additive treatment can have benefits. Fuel treated by its producer and an additive poured into the tank later are not automatically interchangeable.
| Possible benefits of suitable treatment | Risks of unsuitable use |
|---|---|
| Keeping the fuel system clean and limiting deposits. | An unapproved product can damage the engine or emissions system. |
| Protection against corrosion. | Metallic octane additives can damage the engine and catalytic converter. |
| Improving diesel ignition or low-temperature properties. | An unsuitable combination of winter additives can impair fuel filterability. |
Effects depend on the fuel composition and exact additive and cannot be promised for every product.
Use aftermarket additives only where the manufacturer permits them for the exact vehicle. Some manuals expressly prohibit adding them to diesel. Follow the dose for an approved product and do not combine additives without verifying compatibility.
For winter operation, use diesel suitable for the expected temperatures. Never dilute diesel with petrol.