Quick Summary:
- Check the fuel door sticker or handbook for the minimum octane.
- In California, ‘Regular’ usually means 87 octane at the pump.
- If the car requires 91, use Premium, not Midgrade.
- Keep itemised fuel receipts showing date, location, gallons, and grade.
Picking the right petrol grade in California is one of those small details that can prevent bigger hassles later, especially with a car hire. The pumps show numbers like 87, 89, and 91, and if you are used to UK labels you may wonder whether 87 is too low, whether 91 is “safer”, or whether the wrong choice could cause charges when you return the vehicle.
The good news is that most mainstream hire cars in California are designed to run happily on 87 octane, which is labelled “Regular” in the US. Some higher performance models, certain turbo engines, and a number of larger SUVs may specify a higher minimum, often 91 in California. Your job is to confirm what your specific vehicle requires and then keep simple proof that you refuelled correctly and at the right time.
Why petrol grades look different in the US (and why that matters)
In the US, petrol grades are shown by octane numbers such as 87, 89, and 91. These numbers are based on an octane rating method used at US pumps, so they look lower than the 95 and 98 you might recognise from the UK. This does not mean US petrol is “worse”, it is just displayed differently.
For a California car hire, you do not need to convert numbers. Instead, treat the number on the pump as the reference point, and match it to the vehicle’s minimum requirement. If the fuel door says 87, you can confidently use Regular 87. If it says 91 recommended or 91 required, choose Premium 91 in California.
Where to check the required fuel in your hire car
Do not guess based on the model name alone, because trim levels and engines can differ. The most reliable places to confirm the required fuel are on the car itself, not on the pump label.
1) Fuel door sticker
Open the fuel filler door and look for a label or sticker. Many vehicles clearly state “Unleaded fuel only” and then give a minimum octane number, for example “87 (R+M)/2” or “91 recommended”. Some vehicles also mention “Premium unleaded only”. If you see “Premium recommended”, it means the engine can run on Regular but may deliver slightly less performance or economy. If you see “Premium required” or “91 minimum”, follow that instruction.
2) Handbook in the glovebox
If the fuel door is unclear or the label is missing, check the owner’s manual in the glovebox. Look in the “Fuel” or “Specifications” section. You are looking for “minimum octane rating” and any notes about premium fuel requirements. This is also helpful if you are unsure whether the wording “recommended” is a preference rather than a strict requirement.
3) Dashboard message or infotainment notes
Some modern cars show guidance in the driver information screens, especially if the vehicle has been set up with certain service reminders. This should never be your only source, but it can reinforce what you see on the fuel door label.
What ‘Regular’ means in California (and why 91 is not always “better”)
At most California stations you will typically see:
Regular, usually 87 octane.
Midgrade, often 89 octane.
Premium, commonly 91 octane in California (93 is more common in some other states).
If your car hire specifies 87, buying 91 does not usually provide a meaningful benefit for normal driving. Many engines are tuned for 87, so premium can be a needless extra cost. Conversely, if your car requires 91, using 87 can lead to engine knocking, reduced power, and the car compensating by retarding ignition timing. Modern engines can protect themselves, but you may notice poorer performance, and it is still not ideal to ignore a stated minimum requirement.
When in doubt, follow the minimum octane listed on the vehicle. If it says “87 minimum”, use Regular 87. If it says “91 minimum” or “Premium only”, buy Premium 91.
Common scenarios for travellers using car hire in California
California trips often involve long freeway stretches, hill climbs, and hot weather. None of that changes the octane requirement, but it can make it more obvious when the wrong grade is used, especially on climbs or under heavy load.
If you are collecting a car near a major airport such as San Francisco or Los Angeles, you might be keen to get going quickly. That is fine, just take a moment before your first refuel to check the fuel door label. If you are planning a one way drive through the state, you can compare options for pick-up points like car hire at San Francisco Airport (SFO) or city gateways like car rental at Los Angeles (LAX) and then build fuel stops into your route.
Drivers choosing bigger vehicles, such as an SUV for family luggage or coastal road trips, should be extra careful to read the label, because some larger or more powerful engines can specify premium. If you are comparing sizes around LA, it can help to look at options like SUV rental in Los Angeles (LAX) and then confirm the fuel requirement once you receive your exact vehicle.
How to choose the right pump and avoid misfuelling
Once you know the required octane, selecting the correct pump button is straightforward. The bigger risk is rushing and pressing a different grade than intended, or misunderstanding “Plus” or “Special” branding.
Use this quick method:
Step 1: Confirm the minimum octane on the fuel door (for example, 87 or 91).
Step 2: At the pump, locate the octane numbers first, not the marketing words.
Step 3: Choose the grade that matches or exceeds the minimum.
Step 4: Ensure it is unleaded. Nearly all passenger cars are unleaded only.
Avoid using diesel by mistake. Diesel nozzles are often a different size, but some pumps have multiple fuels in a row, and the green handle does not always mean diesel in the US. If your car hire is petrol, stick with unleaded grades and confirm the pump label before lifting the nozzle.
If the car says “Premium recommended”, should you pay for 91?
“Recommended” is not the same as “required”. For many engines, premium recommended means the car can safely run on 87, but the manufacturer designed the engine to achieve maximum performance on higher octane. If you are keeping costs down on a road trip, 87 is typically fine. If you are driving in high heat, carrying heavy loads, or prefer smoother acceleration, you might choose 91 occasionally. Either way, you are unlikely to have “issues” with the hire provider based solely on choosing 87 when premium is only recommended.
What you should not do is ignore “Premium required” or “91 minimum”. If you see those words, treat them as firm instructions.
What to do if you accidentally use the wrong grade
If you put 87 in a car that requires 91, do not panic. One tank is unlikely to cause damage in modern vehicles, but you should minimise heavy acceleration and high load driving. When you next refuel, switch to the correct grade and consider filling up earlier than usual so the mixture returns to the higher octane sooner.
If you put diesel into a petrol vehicle or petrol into a diesel vehicle, that is a different situation. Do not start the engine. Contact roadside assistance immediately and follow the procedure provided by your hire agreement.
Receipts to keep, and what details matter
Receipts are a simple way to avoid disputes, especially for “full-to-full” fuel policies where the vehicle must be returned with the same fuel level as collection. Even when you return the car full, a receipt can help if there is a later query about timing, location, or fuel grade.
Keep an itemised receipt that shows:
Date and time, ideally close to the return time.
Station address or city, helpful if you returned near an airport.
Fuel grade, such as 87, 89, or 91, or “Regular/Premium” with octane.
Gallons and total amount, showing you actually refuelled.
Last four digits of card, useful for matching payments.
If the pump or terminal only prints a minimal receipt, go inside and request an itemised copy. You can also take a clear photo of the receipt and the fuel gauge at the time you refuel, which can be handy if the paper fades.
Practical refuelling tips for airport returns in California
Airport areas can have higher fuel prices, but returning without refuelling can cost more if the provider charges a premium refuelling rate. Build in time to refuel within a few miles of the return location and keep the receipt.
If you are returning a larger vehicle or travelling with a group, allow extra time because some stations near airports have queues. This is particularly relevant around LA. If you picked up a van for a family trip, such as via van rental in San Jose (SJC), remember that bigger tanks can take longer to fill and the pump may shut off early if the nozzle angle is awkward.
Does choosing 91 affect the hire company’s requirements?
Hire providers generally care about two things: that you use the correct fuel type (petrol versus diesel) and that you return the vehicle according to the agreed fuel policy. They typically do not check octane receipts for every return, but it is still sensible to follow the manufacturer’s minimum octane requirement because it reduces the chance of performance issues and complaints during your trip.
Where octane can matter is if a vehicle experiences noticeable knocking or a check-engine light after being fuelled, which can delay your journey and lead to inspection. Using the specified minimum grade is the simplest way to avoid that risk.
One last check before you drive away
When you collect your California car hire, take 30 seconds to do two checks before leaving the lot: confirm whether the vehicle is petrol or diesel, and read the minimum octane requirement on the fuel door label. Those two details, plus keeping your final receipt, cover the most common fuel related issues travellers face.
FAQ
Q: Is 87 octane the same as UK 87?
A: No. US pump numbers use a different octane rating method, so they appear lower than UK 95 or 98. Follow the number shown on the car’s fuel door label.
Q: In California, does ‘Regular’ always mean 87?
A: Almost always, yes. Most California stations label Regular as 87, Midgrade as 89, and Premium as 91. Check the octane number on the pump to be sure.
Q: If my hire car says ‘Premium recommended’, will 87 cause problems?
A: Usually not. Recommended means the engine can run on 87, but may perform best on 91. Problems are more likely when premium is required, not merely recommended.
Q: What fuel receipt should I keep when returning the car?
A: Keep an itemised receipt showing the station location, date and time, gallons, total paid, and the octane grade (87, 89, or 91). A photo backup helps.
Q: Should I use 91 “just in case” to avoid disputes?
A: Only if the vehicle specifies 91 minimum or Premium required. If it specifies 87, paying for 91 is generally unnecessary, and it does not replace the need to return the car with the agreed fuel level.
