What grade of gas do you use???
 

I have an 88 vert, NA and have read differing opinions of what kind of gas to use from 87 to 93

Can someone clear this up??

With an NA the lower the grade of fuel the better so be sure to use 87. TII's need the higher octane and should never be run with anything lower then 93 octane.

Here in Aus,
I only use 98 oct :)

In my TII, 93 to 116.

:D in my streetported TII I run 87 octane, with no detenation and 7-8 psi boost :)

What octane do owners of 89-91 NA use? This engine comes stock with a 9.7:1 CR. IS this later engine equipped with a knock sensor? Does the computer alter the ignition timing based on a lower or higher octane?

TODD

i use 93 when i find it. but i do not go lower than 91 on my bported t2.

Bottom line is, ALL N/A's only need 87 octane, period. If you are running boost it's another story, but N/A's regardless of year only need 87 octane.

Some of you scare me by running your TII with 87 or 91 octane. Not saying that I know everything about owning a turbo, but when I do own one, I know I sure as hell will only use 93 or higher. I dont see the point of risking detenation.

well in the bay area we only have 91 octane readily available, but for the NA lowest octane possible.

I run Jet-A

SImple as this, and THIS HAS BEEN ASKED BEFORE!!!!!!!!!!!!



N/a the LOWEST YOU CAN FIND

TII's are meant to run at 87 octane but if your pumping up the boost and modding get the highest you can find.


An N/a should never need high octane unless you did some timming changes which are too much for 87 oct.

93 octane only.

Does this mean you will make runs south of the border and pick up the good stuff ( I mean the low octane) from down there:) You can ship it to the NA members:)

JAmes

the mazda bible says 87 for n/a and 93 or higher for turbo.

i'm assuming that when i supercharge my n/a i'll need to go for the higher octane as well. which is too bad - like gas prices aren't high enough for 87 octane!

87 octane, always and forever

-Markus

"I use to run 93, cause i was dumb and didnt know anybetter. after talking to some folks i learned" CHEERS!

An N/A will make just as much power, leave less deposits, and run more smoothly on higher grade fuels.

You just have to question cost vs. gain.

I run 93 Oct only at 6K ft elevation, which is equal to running 95 Oct at sea level.

87 octane when I had my NA. 91 for my Turbo II.

Totally false. It's not your fault, the big oil companies spread the BS so they can get more money out of you. Please read:
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

Some of you scare me by paying too much for gas that does you no good whatsoever. Higher octane is only required for modified cars, or for engines that are not running well.

Which "mazda bible"? The owner's manual states 87 octane (US).

I would like to see that. :D

I run 93 in my n/a?? it works way better than 87, and i get better gas mileage with it too. and my car pulls harder too. why arent you supposed to use it?

first, how many times has this type of thread been brought up, not to get on ur ass JPA but this has been brought up numerous times. second, Impreza2RX7, i dont know know what u mean with ur post, but changes in elevation wouldnt mean its different octane. if anything it might feel like it. but even then i wouldnt know. the higher alt would just mean that the air is a lot less dense then it is at sea level, which u would feel a decrease in performance, but that different info from what is being discussed. so sorry but please explain to me why 93 octane at 6k ft = 95 octane at sealevel.

and from personal experience the NA loves lower octane atleast on mine. when i first got my car i thought id throw in a full tank of premium, just to clean out any deposits or what not. and it ran fine. but this was my first time owning a 7 so i didnt know how it was supposed to run. then after that tank was done i put 87 in and damn it made a huge difference. my butt dyno says i must have got some good usable HP back.

Thanks for your input Mighty Mouse. I searched first but did not find anything.

You probably have massive carbon build up. lol

Try a lot of high rpm driving with the highest octane SHELL gas you can find and then gradually go down to mid grade and then lowest grade available. If the problem persists I dunno try the water trick.

Santiago

Having both 13B N/A and a 13BT car, their respective (canadian) owners manuals state:

87 Octane
91 Octane

I have never seen that 13BT's where designed to run on 87, like a previous poster said...:confused:

Evil Aviator-quoted the US manual. That is good enough for me. :)

Oh, I'm not doubting EA's sources. In fact, he's one of the most reliable people on here.

Its just interesting to note that the same car, can have such a variation in recommended octane...

Lol, one of the few folks that would even know what Jet A is:)

Oh yea. On the '86 Base I run 87. Before I was educated I ran 91. And when I switched it was noticeable.

On the 91 TII I run 91 octane.



James

I believe octane ratings where differn't for the turbos depending on the year 87-88 lower compression rotors, less octane, 89-91 high compression, higher octane makes sense. Though I have never seen an 87 TII onwers manual, just heard through the grape vine that it said to use 87 octane.

Maybe its the fact that I'm street ported and have more volumetric efficency, more cooling due to more suface area of the intake and exhuast ports.

Also maybe its because I'm running 4 trailing plugs (colder spark less chance of detenation)

Or is it because I'm running a walbro fuel pump?

Whatever it is my car runs the best on 87 octane pushing 7-8psi, intake, 2.5 full exhuast, port matched turbo runners and ported wastgate.

I just ran it at the track on the 87 and ran a 13.5 at 103 with a bad clutch I was still running rich too, full boost at 3000 rpms and it holds it untill 7000 :)

Octane lowers the flash point of fuel. The lower the flash point, the higher the resistance to pre-detonation, or pinging.

The higher the absolute pressure of the air fuel mixture, either through higher compression ratio, boost, or volumetric efficiency, the more propensity an engine has to pre-detonate.

In higher elevations, engines have less volumetric efficiency, and require less octane due to lower combustion pressure.

Rotary engines, due to their combustion chamber rotating on its axis, have high resistance to detonation, and require only low octane fuel.

Jet-A, which is really just kerosene, has a VERY low flash point, wouldn't ignite by the spark plug, and therefore wouldn't even start the car.

very nice observations OnlineAlias :D

Wait :scratch:

WOuldn't octane make the flash point higher? meaning the pre-ignition temp would be higher thusly resisting detonation MORE? I am just trying to understand this don't take it as an arguement :)

no no, a high flash point is from lower octane, lower flasher point is from higher octane

kinda like leaner is hotter combustion
and richer is cooler combustion

Is that octane rating Research Octane Number (RON) or Pump Octane Number (PON, aka the R+M/2 method)? Also, Canada may have less quality controls on their petroleum products, and therefore Mazda may recommend a higher octane for safety.

I always recommend that non-US forum members list their country of origin in their "location" at the left of the screen because otherwise everybody assumes that you are in the US, and some things are not the same. For example, the US octane rating is not the same as most non-US octane ratings, the US quart is not the same as an imperial quart, $1 USD is not the same as $1 CAN, etc.

I have owned both an 88 NA and TII, and can verify that the US manual lists a minimum octane rating of 87 (PON). Jerry Harding has verified the same with the US S5 manual.

Assuming that the engine is somewhat stock and in good running condition, it will work just fine on lower-octane fuel. There is nothing wrong with using higher-octane fuel, other that it's a waste of money if you don't need the extra anti-knock properties. I'm not sure about the other countries, but the US has certain standards for fuels, and all US octane grades have detergents, additives and whatnot, but the oil companies only advertise this about their high octane fuel in an attempt to make the consumers think that only the expensive fuel is good for their engine. Higher octane IS a good idea for some modified engines, some engines that are in poor shape and/or out of tune, and all highly-boosted engines.

The fuel octane rating isn't raised, the octane requirement of the engine is lowered. Does that make more sense now? Anyway, it's not necessarily a whole 2 octane numbers, and may be next to nothing, depending on the engine and amount of altitude change. Also, because of this octane requirement reduction, some oil companies re-state their octane rating to a higher number in high altitude areas, so you need to be careful about what you are actually putting in your tank and where you drive after filling up the tank. ;)
http://www.imoc.co.uk/technical/article/octane.htm#q31

good write up evilaviator

I've been running regular in mine (S5 NA) for about 4 or 5 months now, and just last week I put in some midgrade just to see what would happen. It seems to idle a little more smoothly, and pull a little harder. Is this change only temporary? Should I switch back to regular?

I've always use mid-range gas and works great. I tried higher octaine gas, but, there were no impressive improvement. So, I stick to the mid range.

okay now a REAL question j/k,

how many points are there to an octane number? when you buy octane additives it say will raise up to 17 points or 1-2 octane numbers

The way I understand octane booster, is one bottle is one point. So if you need more than one point, use more than one bottle.

One point = 0.1 octane number. Therefore, 17 points = 1.7 octane numbers, which would in fact fall between the 1-2 octane numbers as you have stated. Most octane boosters only add 4-7 points (0.4-0.7 octane number) increase. For example, adding a 7 point octane booster to your 91 octane gas would yield 91.7 octane gas. Obviously, this is a rip-off at $8 per tank for the treatment. Therefore, save your money for something that is actually useful, and leave the octane boosters to the Ricers. ;)

If you add a bunch of bottles of octane booster to your fuel tank, it can eat away your fuel system, and possibly harm your engine. Not good.

BTW, if you guys ever want to know what they put in this junk, just ask for the MSDS (MATERIAL SAFETY DATA SHEET).
http://householdproducts.nlm.nih.gov...ueryx=Additive

I run 91 -93 ocatane because i am boosting 15psi!!!
but if was running stock it would be 87-89 octace for me that is here in canada!
And as far as i understand the us and canadian octance per fluid once is the same regulations. I could be wrong if so somone please correct me, but last i read it was the same! just a little bit of info

Hey, don't drag me into this! :)

Yes, the US S5 manual (my 1991 to be exact) states "Your new Mazda is designed to obtain maximum performance with UNLEADED GASOLINE with an octane rating (anti-knock index) of 87 or higher (using R+M/2)."

It makes no differentiation between turbo or non, but they do say "or higher." Take it for what it's worth. Mazda says your stock car can run on 87.

94 Octane nothing less on my TII

89 octane for my S4, cuz anything less and she runs like crap.

i run 89 on my s4 na only because i have my timing advanced 10 degrees. i also use jp-8 when available:D

my N/A worked great on 85. I could actually feel a slight loss in power with 91.

octane RAISES the flash point of the fuel, meaning that it takes a higher temperature to detonate without a spark. also higher octane fuel burns a little slower, and a little hotter than lower octane fuel... I tried running premium (91 here in socal) in my 88 'vert, and it was awful. it idled fine, but i got alot of surging in the acceleration (less power, and really uneven). I tried it to see if the increased pressure (from higher combustion temps) outweighed the slower burn rate, and apperently it didn't. If I was boosting or messed with the timing so it started burning earlier I would try it again to compare to regular (87), but until I do my turbo swap I'm stickin with regular... ;)

oh blackrx7, you said that you are running 4 trailing plugs for lower spark temp. why would you want a lower spark temp? once it sparks, the fuel is supposed to burn... I'm not trying to flame, I just wanted to understand cuz maybe you know something I dont...

heh... 87 here on my NA, to poor for 91.

What is the difference between 89 and 93 ?

Same!:)