Soapflake

I run 89 mostly and I don't notice a performance loss. I tried a couple tanks of 87 and it didn't really feel as good. Didn't idle the same, engine was a little raspy and it seemed to have had an effect on acceleration.

I too have noticed that I get 10-15 more miles on a tank of 89 than I do a tank of 93, both bought from the same station.

As for me, I run 89 regularly and run 93 once every 4 or 5 fill-ups.

RotaryP7

I use Diesel. But then again, that's just me..

Renesis07

iTrader: (1)

I use sugar. The rotary loves it.

swoope

iTrader: (5)

ok,

the secret is using a very good quality 87.i have been using it for 88k miles. with 4oz of premix and lately 2oz of fp +.

most of the time i get ~21 mpg. mostly hi way driving..

note to all.. track days get a 93 oct. and 8oz of premix..

beers

kartweb

I went for about 3000 miles mixing E85 with E10 to get an E20 blend. Runs excellent and gets about 1/2 an MPG lower mileage. Suddenly E85 jumped in price a few weeks ago. No problem I just bought a barrel of ethanol, traded my empty barrel of T111 (from kart racing) for the deposit. Price per gallon was a hair over $2, no road taxes.

Also I learned that in Texas when it says 10% ethanol, that usually means 12-15% ethanol. 87 grade is also closer to 89 grade as they don't lower the octane of the gas despite that ethanol will increase the octane.

After a few calls and emails to Mazda I finally got a response from them. ( I gave them RG's name so they wouldn't void my warrantee in case, knowing he loves ethanol - just kidding RG.) At 20-25% ethanol it won't be a problem. Above 25% it could be a problem. If it trips a code then its outside the closed loop calibration parameters and would pose a problem, otherwise it should be OK.

PSUGreySreet

Not trying to knock you or anything, but think of it this way instead of just "saving 1.25 a day"... Multiply that by 365 and you have saved $456.25 over the course of a year.

How many of you receive your tax refund check at the end of a year, say totaling $300, and are excited to get that spending money that you totally forgot about? Well you have just received a $450 "gas refund" check and if the gas works, why not use it??

superglue

Sir yes sir!!! Standing by for my car to assplode on 91 octane.

r0tor

iTrader: (1)

well i'm not getting 3-4 more mpg from 89 over 93 because of the 89 octane having more enerby... its from better and more complete combustion!

nycgps

iTrader: (1)

I tried some Canola oil lately, hey guess what it made my exhaust smells like roasted Corn !

Huey52

iTrader: (2)

Wow, ain't that the truth.

Higher octane prevents pre-ignition (aka dieseling, ping), therefore as long as your engine runs smoothly you can go with lower octanes. Mine runs fine on 87 without any ping.

Having said that, there is some performance degradation in running the lower octanes, as clearly cited in the owner's manual.

So, your choice - economy or being able to operate a sports car as it was intended.

nycgps

iTrader: (1)

Wrong.

The lower the Resistance, the better the performance.

Higher Octane, unless u're getting a knock, will actually give you *lower* performance.

neXib

I actually doubt there's better performance in 93, may be slightly less in 87, but I'd go with the recommended to be safe. Why? Because with all the emissions crap nowadays I'm sure they'd want to recommend the lowest octane they safely can.

Anyways over here everyone uses 95, as that's the lowest we got. That was like your 91 if I remember correctly.

Huey52

iTrader: (2)

Wow, more dis-information from a generally better informed source.

btw: this from a certified Mazda engine remanufactuer in another thread. A very good reason to give 'er the Premium she deserves (and to run it hard):

"... BTW some advice to all you owners, premium gas is a must and don't be afraid to high rev it at all, [not doing so contributes to] a lot of carbon build up on the side seals (no compression) and the corner seals are also a bitch to get out of the cores due to the carbon build up which is more then likely due to slow city cruising....open her up, she likes it. I figure most of the owners that are causing those issues are probably not familiar with the rotary unlike a rx8 forum by just fyi."

nycgps

iTrader: (1)

There is a federal requirement of cleaning detergent in gasoline, and sadly, years ago they cut the requirements in 1/2 to save oil companies money when the *original* requirement wasnt even enough to began with.

Now, there are only a *few* of the companies out there that has *more than federal requirements* in their Premium gas.

EVEN with the *special* blend of cleaning detergent, its still FAR below what it suppose to have.

So if you're thinking about *every little bit helps* then yeah, Premium does clean better. but alot better? not really.

This engine, Revving it is the key, of which, 95% of Rotary user failed to do so.

GTRay

assuming all other parameters stay equal - which they don't.

you're ignition system is not a static component in the equation. if the computer is calibrated/tuned for premium fuel then it can be assumed that the timing is optimized for that fuel. higher octane fuel resists pre-ignition longer than lower octane rated fuels. it can also be understood that higher octane fuel is more stable as it is ignited - this means it can be ignited sooner. translated into forum lingo - the computer can run more advanced timing on higher rather than lower octane rated fuel. the difference between 89 and 92/93 may not be as critical as the difference between 87 and 89 in the case of the 13BMSPRE. i'm not an expert on the combustion characteristics of specific fuel grades in rotaries or any other engine for that matter but common sense says the sooner you can achieve controled combustion the more likely you are to create higher power or smoother idle.

i've been running 89 exclusively in florida, summer and fall, since our car was new in october 03. no engine problems to date.

Ray

Glyphon

the ECU only adjusts settings if the knock sensor detects predetonation. otherwise, it uses the exact same settings. there is no octane-sensor in the car to "know" before injection what grade of fuel is in the car. any performance degradation would be a reaction to a detected ping. no ping, no performance retarding. so, run the lowest octane possible that won't ping.

ken-x8

Higher octane permits more ignition advance, which does translate to better performance. Not necessarily better mileage, but more power. The owner's manual recommends 91 for best performance, but says 87 is OK.

If you run 87, as long as your car's sensors and computer are working you won't have pinging. Whether you notice a performance change depends on your stopwatch and/or butt.

Ken

alnielsen

iTrader: (4)

Close, the PCM will only retard the timing if it senses pinging. No pinging, max timing. Like it was said previously, the car can't sense what octane gas you are useing. It can only sense ping.
The additives in gas will mainly just clean deposits on the injector. They won't do anything for carbon in the combustion process. This is something that the alcohol, now in the fuel, will do also.
The reason some find better performance with lower octane fuel is alcohol is used as an octane booster. And alcohol has less power than gas.

BTW: I work at BP. I may be a computer nerd, but I have contact with the researchers.

Raptor75

The only difference I found by moving to 87 was an extra $3.50 in my pocket at the end of the fill up and guess what it still ran just like a sports car.

Huey52

iTrader: (2)

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.

You may use a regular unleaded fuel with an Octane Rating from 87 to 90 (91 to 95 RON) but this will slightly reduce performance.

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.

Socket7

I once filled up with 87. My renny got out of my 8, punched me in the face, then told me that if anyone asked about why I had a black eye, I was to say that I fell down the stairs.

Glyphon

yup. we all have the manual too.

the only time you will have slightly reduced performance is if the knock sensor detects pre-detonation. no ping, no performance loss. there isn't a sensor that detects what type of fuel is in the tank. any performance retarding is 100% reactionary, based solely on the detection of pinging.

they also never define what slightly reduced performance is. could be 1/4hp. could be 5hp. regardless, you most likely won't feel slightly reduced performance in daily driving.

you might see that on a drag strip or on a track, but in those situations, you should definitely be using higher octane fuel because the prolonged running at high rpms will increase engine temps and increase the likelyhood of getting pre-det.

same applies if you live in a really hot local. i've yet to notice any slightly reduced performance, even on days where it was over 100F.

regardless, it isn't potentially bad for your car until the octane goes below 87. notice how knocking isn't mentioned as a concern until less than 87?

alnielsen

iTrader: (4)

That appears to be a quote from the owners manual.
Remember, Mazda had to make a change to the original PCM calibration to make emissions and this reduced the original listed horsepower. Mazda has many masters to serve, regulations to abide by, to produce a car legal for sale. Mazda also recommends 5W-20 oil, which many say is too light for the car. And then there is the conventional vs syntentic oil debate. This is just another one of those. Mazda has to specify something for legal reasons, when something else may work or be better. Remember, Mazda had to make a change to the original PCM calibration to make emissions and this reduced the horsepower.

Huey52

iTrader: (2)

Yes, manual quoted. Just trying to stay in the spirit of the original question.

The bottom line is 87 - 91 octane is fine. Any higher is a waste of money and any lower invites knock. Personal preference within that range.

AJ's Shinka

Only JP-8 in my rotary rocket. Nothing but the best.