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RON petrol grades at a glance
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| Label | What it means | Typical driver action |
|---|---|---|
| 95 RON | Standard UK unleaded petrol, commonly sold as E10. | Suitable when your car permits 95 RON and is compatible with the pump’s ethanol label. |
| 97 RON | A super unleaded grade above standard 95 RON. | Check your minimum: 97 RON does not meet a 98 or 99 RON requirement. |
| 98 RON | An octane requirement found in some vehicle handbooks. | If 98 RON is required, choose a compatible petrol rated at least 98, such as a suitable 99 RON product. |
| 99 RON | High-octane premium petrol sold by selected UK retailers. | Use it when your car or ECU tune asks for it, or compare the added cost if it is only optional. |
| 101 or 102 RON | Specialist high-octane fuel, usually not a normal everyday forecourt choice. | Use only when your vehicle, tuner or motorsport supplier specifies it. |
Is E5 the same as RON 99?
No. E5 and E10 describe ethanol content. E10 petrol can contain up to 10% renewable ethanol. E5 petrol can contain up to 5% ethanol.
RON describes octane. E5 is not a promise of 99 RON, and it does not mean ethanol-free. Check the octane number and ethanol label independently. Use the GOV.UK E10 compatibility checker if you are unsure about E10.
When does higher RON matter?
RON means Research Octane Number: a measure of petrol's resistance to engine knock. It is separate from the E5 or E10 ethanol label and does not, by itself, tell you the fuel's detergent content.
Minimum permitted is the lowest octane the manufacturer allows. Recommended for full performance can be higher while a lower grade is still permitted. Required means you should use fuel meeting that rating. Read the exact wording for your model rather than assuming every mention of premium fuel means the same thing.
Where to find the right RON for your car
- Check the fuel flap label.
- Check the owner's manual or in-car digital handbook.
- Search manufacturer guidance for your exact model and engine.
- If the car is tuned or remapped, ask the tuner which grade the tune expects.
- If it is an import, use the equivalent UK RON grade specified by the manufacturer.
Is 99 RON worth it?
It can be worth it when the car needs it or can use it for full performance. For a normal car designed for 95 RON, the decision is mostly cost: compare the extra pence per litre against any real change in MPG, then check whether the station is practical for your route.
The 99 RON value guide explains how to compare the price premium with any measured MPG benefit. Once you know the grade you need, find nearby 99 RON prices, search Tesco Momentum 99 or read the Momentum 99 vs Shell V-Power comparison.
RON petrol FAQs
What RON petrol does my car need?
Use the minimum octane listed for your exact model, engine and any ECU tune, and check ethanol compatibility separately. If your car requires 98 RON, a 97 RON petrol does not meet that requirement.
Is E5 the same as 99 RON?
No. E5 means petrol with up to 5% ethanol; 99 RON describes its octane rating. An E5 fuel can have a different octane rating, so check both labels.
Can I use 99 RON instead of 95 RON?
A higher octane meets a lower minimum octane requirement, but the fuel must also suit your vehicle’s ethanol and other fuel specifications. Do not assume that paying more will improve MPG enough to cover the price difference.
Can I mix RON 95 and RON 99?
If your car is compatible with both fuels and each meets its minimum octane requirement, mixing is normally permitted. Do not dilute a required high-octane fuel with a lower grade on the assumption that averaging the labels is sufficient. For a tuned car, follow the tuner’s instructions.
Is RON 101 or RON 102 better?
Not for normal road use unless your car or tuner specifically requires it. Most UK drivers should focus on the grade the car asks for, not the highest number they can find.
Does premium fuel clean the engine?
Some retailers make additive claims for premium products, but RON itself is an octane rating. Treat cleaning claims and octane rating as separate points.