My user manual is confusing. It says the following:

Jan 3, 2025
9:44:20am

UNLVcougar Intervention Needed

“Your vehicle is designed to use only unleaded fuel having a pump octane number ((R+M/2) of 87 (Research Octane Number 91) or higher.”

What does 87 but research octane number of 91 mean?

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UNLVcougar

Bio page: UNLVcougar
Joined: Oct 3, 2001
Last login: Jan 5, 2025
Total posts: 58,369 (2,322 FO)

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Messages

Author

Time

Does putting 91 octane really make a positive difference on your car or is it

UNLVcougar

Jan 3, 9:27am

Depends on the car

PROBcoug

Jan 3, 9:27am

I read your first line as “your attitude.” Was looking forward to hearing how

Traveshamockery

Jan 3, 9:32am

Only in my Porsche and Lambo. Everything else I use 89.

Vincent's Picks

Jan 3, 9:30am

Same. Although 89 in 20 or so vehicles (lost count) is A LOT of octane…

Refugee

Jan 3, 11:50am

I’ve been wondering this as well. Just bought a Land Cruiser and it says premium only. Wondered if it really matters.

Texas Hammer

Jan 3, 9:30am

Actually, it does.

Snipe

Jan 3, 9:38am

Completely unnecessary for most cars.

TANK

Jan 3, 9:32am

Most *boring* cars. FTFY

Superkid

Jan 3, 9:40am

If your vehicle calls for it, it's best to use it. If not, you likely won't see any difference.

John Doe

Jan 3, 9:32am

It's engine specific. Use whatever the manufacturer recommends for the specific vehicle.

kccougar

Jan 3, 9:33am

My user manual is confusing. It says the following:

UNLVcougar

Jan 3, 9:44am

R+m/2 is what is displayed on the pump. There are 2 different tests. The number is the average of the 2.

jollaksentie

Jan 3, 9:47am

👆🏻This. So the short answer is you can buy the gas listed as “87” at the pump and you’re good to go.

mvtoro

Jan 3, 11:09am

They are two different rating systems. In the US we typically use the R+M/2 method

kccougar

Jan 3, 9:47am

Depends on the compression ratio. High octane auto-ignites slower,

Kilgore Trout

Jan 3, 9:33am

Yes. Some engines are designed for it. Computers can adjust timing

reddead

Jan 3, 9:33am

It is absolutely necessary!

Superkid

Jan 3, 9:34am

Checking the CB archives, looks like this topic is on about a 10-yr cycle. 2025, 2014, 2004...

kccougar

Jan 3, 9:35am

There is no more energy in higher octane fuel. The rating indicates the stability of the fuel. If the rating is too low

jollaksentie

Jan 3, 9:40am

It's all about pinging and knocking

justAnotherCoug

Jan 3, 9:40am

I notice a difference in my 5.0L f150 when I

The Pope

Jan 3, 9:42am

I also have a 5.0 F-150, do you use 87 when you're not towing?

mang

Jan 3, 12:14pm

Yeah, just regular ol’ 87. I’m in PHX, so my elevation is

The Pope

Jan 3, 12:55pm

Every car will give you the optimal grade to use. It is best to

IceBlue

Jan 3, 9:48am

I have owned several Nissan 3.5/3.7 cars that if you do not use premium they run

Ycrazy

Jan 3, 9:50am

NO. not at our elevation.

BYURider

Jan 3, 9:55am

Incorrect, though elevation does play a part. You won't see many (any?) vehicles sold today that recommend 85 octane

kccougar

Jan 3, 10:03am

It’s based on the compression level that your engine runs. High-compression engines can cause premature ignition of the

mvtoro

Jan 3, 11:05am

Great info. I've wondered this for years and gone back and forth. Is the owners manual the only place you'll find it?

BlooGeek

Jan 3, 12:22pm

Easy to Google.

mvtoro

Jan 3, 12:25pm

Hey! Whaddya know...2020 Palisade requires 87. My gas spending just went down.

BlooGeek

Jan 3, 12:31pm

Same for mine but what I was already using most the time.

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