87, 89, or 91 octane?

[RabidRich]

So i recently purchased a new Mazda 3 GT...sweet ride, loving it. However I just noticed in the user manual (after a few fills of course) that it recommends 91 octane, and 87 should only be used in an emergency. When i speak to the dealer, they laugh and say the 87 is fine. Any thoughts on this one :?:

[DragonZealot]

Go with the owner's manual.

The engineer who designed the engine is more knowledgeable than the nobody in the dealership.

[GoiNGPoSTaL]

Did you buy the MazdaSpeed 3 GT or just the regular Sport GT? If it's just the regular Sport GT are you sure you're reading the part about the Sport GT and not the Speed 3, most manuals have all the models in the same book?

[VorteC]

I doubt a normal Mazda3 needs 91 octane. Even if it does recommend 91, you will be able use 87, and maybe lose a little mileage.. but you save 10% @ the pump anyways :P

[skidz88]

Umm, go with the manual. It's a dumb question really. Eventually, using 87 will cost a lot of money when you need a new knock sensor and your motor is pinging. And you get poor gas milage. Now, is that really worth saving $5 at the pump?

[ES_Revenge]

The Mazda3 manual says to use 91 for a normal 2.0 or 2.3 engine? Are you sure you're not talking about RON (which is what they use in Japan and is different from our octane numbers here)?

91 RON is the same as 87 US/Canadian Pump Octane Number ;)

[xg3]

been running 87 octane on my mazda 3 for 3 years..
i laugh too if u fill it up with 91.

[mr_raider]

From YOUR manual:

2.3-liter turbocharger engine
Your Mazda will perform best with fuel listed in the table.
Fuel Octane Rating* (Anti-knock index)

Premium unleaded fuel 91 [ (R+M)/2 method] or above (96 RON or above)

* U.S. federal law requires that octane ratings be posted on gasoline station pumps.

This vehicle is designed for and requires use of premium unleaded fuel. If 91 octane fuel [(R+M)/2 method] (96RON) is not available, gasoline as low as 87 octane [(R+M)/2method] (91RON) can be used temporarily for emergency purposes. Use of gasoline lower
than 91 octane [ (R+M)/2 method] (96RON) can decrease performance during its use.
Refueling the vehicle with the correct octane fuel a couple of times will restore vehicle performance.

Except 2.3-liter turbocharger engine

Your Mazda will perform best with fuel listed in the table.
Fuel Octane Rating* (Anti-knock index)
Regular unleaded fuel 87 [(R+M)/2 method] or above (91 RON or above)

* U.S. federal law requires that octane ratings be posted on gasoline station pumps.
Fuel with a rating lower than 87 octane (91 RON) could cause the emission control system
to lose effectiveness. It could also cause engine knocking and serious engine damage.

[tugzy]

REAR YOUR OWNERS MANUAL CAREFULLY... use what it recommends....done

[i3_dawg]

the user manual is your friend, but i think the mazda 3 2.3L n/a uses 87 octane. But its best to check with the manual.

[Pete_Coach]

As the others have said, read and follow th directions and instructions within the manual.
The reason fro using 91 octane is to ensure the engine performance is as per the specs. If you do choose for whatever reason to use a lower octane rating the ECU (engine control unit or whatever Mazda calls the computer) will detune the engine and cause you to lose performance and power. The computer does this almost immediately. It will program itself back once you return to using 91 but it will take several tanks fulls or 91 to get it working properly again.Yes, damage can be cause by prolonged use of the lower octane fuel.
This forum has had innumerable posts on octane in fuels so please search and read those rather than re-opening a very divisive and opinionated topic.

[Dixon007]

The MazdaSpeed 3 or 6 uses OCT 91
Regular mazda 3 such as 2.0 or 2.3 engines uses 87. i have my mom's manual book here and it says 87 for her 2005 mazda 3 . i think u have the mazdaspeed 3 book.
87
So i recently purchased a new Mazda 3 GT...sweet ride, loving it. However I just noticed in the user manual (after a few fills of course) that it recommends 91 octane, and 87 should only be used in an emergency. When i speak to the dealer, they laugh and say the 87 is fine. Any thoughts on this one :?:

[malaco0219]

The MazdaSpeed 3 or 6 uses OCT 91
Regular mazda 3 such as 2.0 or 2.3 engines uses 87. i have my mom's manual book here and it says 87 for her 2005 mazda 3 . i think u have the mazdaspeed 3 book.
87

Correct me IF i'm wrong, I thought MS6 and MS3 require 93 Octance? Friend owns a MS6 and always complain about driving far to Sunoco to get 94, and sometimes he just gets 91 with octane booster.

I also remember Lumlum103 mentioning he said he used 91 once and experienced a power loss?

[KawaiiTentacleBeast]

MS3 is 91:

http://stg.mazdausa.com/MusaWeb/pdf/quicktips/2007_MAZDA3_QT.pdf

Apparently MS 6 needs 93 Octane.

[enforcerviper]

According to mazda usa... turbo model:

Use 91 octane or above premium unleaded gasoline only, extra fuel additives are NOT recommended

http://stg.mazdausa.com/MusaWeb/pdf/quicktips/2007_MAZDA3_QT.pdf

[ES_Revenge]

Correct me IF i'm wrong, I thought MS6 and MS3 require 93 Octance? Friend owns a MS6 and always complain about driving far to Sunoco to get 94, and sometimes he just gets 91 with octane booster.

I also remember Lumlum103 mentioning he said he used 91 once and experienced a power loss?

There's likely some spark ****** or boost reduction with lower octane fuels, sure. Engine management may allow for more advanced spark and higher boost levels when you put 93 in there.

[RabidRich]

First off, this forum and it's users are the best. I posted the question, went off to do some grocery shopping...and came back to a gambit of information. Much appreciated. However, I will have to admit I am still not sure...

Ae read by what was posted by mr. raider (thanks for typing that out..its exactly what is in my manual), the 2.3-liter turbocharger engine requires 91 octane. If I have the Mazda 3 GT (not sport), then do I have a 'turbocharger'?

And what surprises me is that I called two mazda dealers mechanics, and both said 87 is all i need.

[Andro]

First off, this forum and it's users are the best. I posted the question, went off to do some grocery shopping...and came back to a gambit of information. Much appreciated. However, I will have to admit I am still not sure...

Ae read by what was posted by mr. raider (thanks for typing that out..its exactly what is in my manual), the 2.3-liter turbocharger engine requires 91 octane. If I have the Mazda 3 GT (not sport), then do I have a 'turbocharger'?

And what surprises me is that I called two mazda dealers mechanics, and both said 87 is all i need.

NO, only Mazdaspeed 3 has it from the current mazda 3 lineup.

[RabidRich]

Thanks Andro....and I just found this information on a website, which I guess answers my owen question...no the M3 GT is not turbocharged, thats the sport. So final conclusion, my 87 octane is fine.

"The GT models use a 2.3-litre four-cylinder engine, with five-speed manual or optional five-speed automatic."

"The Mazdaspeed3 uses a turbocharged 2.3-litre engine with six-speed manual only."

Thanks again for the responses.

[mr_raider]

Ae read by what was posted by mr. raider (thanks for typing that out..its exactly what is in my manual), the 2.3-liter turbocharger engine requires 91 octane.

I didn't type it out. I went mazda's web site, downloaded your manual and copy/pasted the info in the hopes that it end discussion and answer your question. I was surprised to see specualtion continue on!

[malaco0219]

There's likely some spark ****** or boost reduction with lower octane fuels, sure. Engine management may allow for more advanced spark and higher boost levels when you put 93 in there.

Interesting, so thats like the 2.0T engine on the GTI and A4.. I remember reading that on their websites..

[hytong]

it can also dump excess fuel into intake tract / cylinder (direct injection) to cool down intake charge

[RabidRich]

Well even if you didn't type it out, it still took some effort on your part...much appreciated. I then ran out in the cold in my jammers to grab the book to re-read it. ;) The 'turbocharged' is what threw me off.

[Jeff-TheBiz]

So i recently purchased a new Mazda 3 GT...sweet ride, loving it. However I just noticed in the user manual (after a few fills of course) that it recommends 91 octane, and 87 should only be used in an emergency. When i speak to the dealer, they laugh and say the 87 is fine. Any thoughts on this one :?:

The manual says you should use 87 octane only, in fact unless your 3 is a Mazdaspeed3 you do not need to you 91.

just read all the replies... well covered.. done

[kleptodathief]

sunoco 94 FTMFW!!! don't really wanna post wot speed i got up to but WOW is all i can say! :cheesygri

[skidz88]

sunoco 94 FTMFW!!! don't really wanna post wot speed i got up to but WOW is all i can say! :cheesygri

Are you trying to attribute a top speed you attained to Sunoco 94 gas? LOL

[mr_raider]

Are you trying to attribute a top speed you attained to Sunoco 94 gas? LOL

No dude, for that you NAWSS!!!

[kleptodathief]

ya skidz: i had this dream where i got up to over 200klicks so 'effortlessly' using sun94 :idea: :D

i'd never do NAAAAAWWWWWWWWWWWWWWWWWssssssssssssss, my pos tranny wud blow lulz

[Pete_Coach]

it can also dump excess fuel into intake tract / cylinder (direct injection) to cool down intake charge

You are kidding right? Excess fuel into the cylinder?

sunoco 94 FTMFW!!! don't really wanna post wot speed i got up to but WOW is all i can say! :cheesygri

i'd never do NAAAAAWWWWWWWWWWWWWWWWWssssssssssssss, my pos tranny wud blow lulz
How old are you really? 14?
Anyone who knows even the least bit about fuel and fuel management would tell you that higher octane fuel in an engine not designed for it will not only make it run rich but perform worse. And the transmission???

[KawaiiTentacleBeast]

You are kidding right? Excess fuel into the cylinder?

He's right. That's exactly how GDI engines like the Mazda DISI work. Under light loads they can run ultra lean too. 1400 psi fuel injectors are great. :lol:

[squireglig]

Correct me IF i'm wrong, I thought MS6 and MS3 require 93 Octance? Friend owns a MS6 and always complain about driving far to Sunoco to get 94, and sometimes he just gets 91 with octane booster.

I also remember Lumlum103 mentioning he said he used 91 once and experienced a power loss?

Yes the speed6 recommends 93, and 91 is minimum. The ECU will lower or cut boost on lower grades of gas (including 91).

[hightech]

There are 2 words that are very important in the owners manual:

Recommended - Means that you SHOULD follow this for best results

Required - Means this is what you MUST do for proper vehicle operation.

Most high compression engine/performance oriented cars, will "recommend" premium fuel. This gives the engine maximum power/performance for the rated HP on the engine. Some very high end vehicles (Porsche, Corvette, BMW, etc.) will state that it "REQUIRES" premium grade fuel.

You can run 87 Octane (i.e. regular Unleaded), but be aware of the following:

- The engine will not be running at max power (i.e. maybe 2 to 3 HP less then what is stated)
- The engine will retort the timing to prevent the spark (i.e. you may hear engine knocking on hard acceleration which could damage the engine).
- Regular Fuel may not have the same amount of fuel additives which may require for more frequent fuel system cleanings.

Some cars are more sensitive to fuel grade depending on the environment temps. I recall reading a long term test of a 2001 Camry V6 when the reviewer noticed a "hard start" situation when running regular fuel. By changing fuel grades to premium, he did not have this problem. I am not sure if it was the fuel grade that in fact caused the issue, or the brand of gas, or bad gas quality in the previous fillup.

If you are a hard driver, and push the engine often, put load on the car, etc., then premium fuel is ideal. If an engine is stressed due to lower octane, it can shorten the useful life of the car in time. I always prefer to follow the recommendation, for better trouble free driving. If you can't follow the recommendation, then look at vehicle where you are more likely to follow recommendations.

On my 02 Camry V6, Toyota "recommends 91 octane for maximum performance". I run Premium fuel all the time as I follow the recommendation, and want to get the most out of my car. If I was leasing a car for say 2 to 3 years, I would just do the required and then transfer any issues to the next owner (hopefully not to their detriment).

[ES_Revenge]

You are kidding right? Excess fuel into the cylinder?
Yep, more fuel and therefore a richer mixture will cool the combustion process and also cool the cat due to lower EGT. Of course this burns more fuel and reduces power, but sometimes it's necessary. In fact almost all modern cars will enrich the mixture slightly to protect the cat with heavy/prolonged high engine output/demand situations.

[Pete_Coach]

He's right. That's exactly how GDI engines like the Mazda DISI work. Under light loads they can run ultra lean too. 1400 psi fuel injectors are great. :lol:

Point was "excess" fuel. There is no such thing, excess fuel alludes to unburnt fuel going into the catalytic converter and causing all sorts of problems. Yes, the Ford Duretec (also knowns as the Mazda M2R) engine is direct injection but that fuel is still controlled and metered so there is no "excess", let alone using raw fuel as a coolant. Any time fuel is directly injected into the engine (as in diesel's) the pressure has to be higher than if the fuel is injected into the airflow. This does not mean that it requires a higher octane.

[ES_Revenge]

Point was "excess" fuel. There is no such thing, excess fuel alludes to unburnt fuel going into the catalytic converter

I think by excess he just meant purposely a bit richer than stoich in order to cool things down, which is indeed done in reality/practice.

[hytong]

:arrowu: thanks

we all agree fuel anti-knock requirement has to do with pressure, since the mixture is a gas, temperature will always be a factor, guess what advance / ****** timing has to do?