RON petrol grades at a glance
| Label | What it means | Typical driver action |
|---|---|---|
| 95 RON | Standard UK unleaded petrol, commonly sold as E10. | Use it when your car asks for 95 RON or standard unleaded. |
| 97 or 98 RON | Higher-octane super unleaded products at some UK stations. | Useful when your car recommends higher octane, or when you want E5 for compatibility. |
| 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. A super unleaded E5 product may be RON 97, 98 or 99 depending on the retailer and product. That is why a premium fuel search should separate Super unleaded E5, RON 97+ and RON 99 instead of treating every E5 price as the same product.
When does higher RON matter?
Higher RON petrol resists knock better. That can matter in engines with high compression, turbocharging, sporty calibration or an ECU remap written for a specific fuel grade.
If the car says 95 RON minimum, 99 RON is usually allowed, but it may not pay for itself through better MPG. If the car says 98 or 99 RON required, use that grade or the higher grade named by the manufacturer or tuner.
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, check the equivalent UK RON grade rather than assuming the pump label matches the original market.
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.
Route & Fuel is built around that final step: compare the price, the extra driving, how far each stop is from your journey and the fill size before choosing a station.
RON petrol FAQs
What RON does my car need?
Use the grade listed for your exact car. If it says 95 RON minimum, standard unleaded is normally the right baseline. If it says 98 or 99 RON, use premium petrol that meets that rating.
Can I mix RON 95 and RON 99?
For most petrol cars, mixing standard unleaded and premium petrol is not a problem. The final tank will sit between the two grades. If a tuned car needs a specific grade, follow the tuner instead.
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.