Nubo

Sure. I've seen people post lap results and they often improve lap by lap. In addition, a lot of what we learn is integrated during sleep. Given similar environmental conditions I'd suspect the second trial would yield better times regardless of which gas was tried first.

In any case, running laps probably isn't the best approach for quantifying the differences you're noticing. There are too many variables and learning/adaptation is just one.

Ole Spiff

I wasn't thinking of laps, but of 1/4 mile runs. I need to find out if they're setup for that at the speedway down the main straight. If not, I may check at the L.A. Fairgrounds in Pomona where they hold the Winternationals each year. That's nothing but a dragstrip; if they allow street cars to do runs I can do them there.

Yeah, if I was doing laps it would not be a good measure. I've driven race tracks before and I know that there are too many variables involved in a lap for that to be reliable to measure a fine difference between octanes. If I was a pro driver who did this every day and could do 20 laps, pull in, have the crew change fuel, then go back out and run another 20 laps maybe it would show a measurable difference. I just want to do some straight 1/4 mile runs.

icyur2

New 2005 Titanium Gray w/Grand RX-8 Package owner!! I guess I'm very lucky because after reading so many threads on how bad some owners are having with their mileage (13+), I'm getting 20 mpg w/91 Octane @Shell (wait until past the E line before refilling): shifting between 3500-3750 RPM. My drives are mainly 95% in-city: 10 min. to work 1-way. Although I'm skeptical, I filled up with 87 and am testing out the theory out there that it works better or gets you better mileage. So far, I do notice that it is more responsive. Will get back after 2 weeks worth of 87 Shell Octane

Ole Spiff

Mileage results after adding the RB CAI and switching back to 87 regular. The first tank that was right after running 91, which included adding the CAI about 1/4 of the way into the tank resulted in a mileage reading of 16.6 mpg which was the worst I've ever measured. The reason? Many many full throttle runs "testing" the performance of the new intake system. I love the way this thing sounds and the car pulls so nicely right up to redline. Definitely not saving me gas though hehehe.

Second tank with the CAI and running 87 I got 17.6 mpg but again, that's with my foot in it a lot...not as bad as the previous tank but I'm having a hard time backing off....this car is such a blast to drive! Also on this last tank we've had very hot weather here....105 the other day and the A/C is on always...from the moment I start the car. So considering everything is against good mileage, 17.6 isn't so bad. For this next tank I'm going to discipline myself to go back to my normal driving routine and see what I get for mileage.

wisconsinben

I know I'm new here and my opinion won't carry as much weight as some others, but I have been trying to decide which grade of fuel to run...and have noticed a similar phenomena. The higher octane gave me SLIGHTLY decreased fuel mileage, and a very SLIGHT throttle reponse hesitation. Not anything major (I didn't think something was wrong with my car) just enough for me to notice.

End: my 2 cents

automaton

I've noticed the complete opposite effect in my 8.

If I top off with 87 (or 89 for that matter) as opposed to the 93 that's available in NY, then I see a significant drop in performance, easily noticeable by me and most passengers. I havn't noticed an enormous bump in fuel economy either, maybe 1 mpg, but, then, I've only ever run one tank at a given time before I get sick of the doggy nature of that tank of gas and switch back to the "good stuff".

My Wife tries to sneak that 87 octane garbage into my tank from time to time and I notice everytime she does it (or so she says).

My money isn't so tight that I worry about 3.00 per fill-up. I'd rather have more fun, and I consider that "fun" to be money well spent... after all, I throw $3 away on more frivolous, less gratifying things on a regular basis.

I used to play around with different brands and grades of gasoline all the time with my WRX, I used to be able to tell the difference between Mobil and Sunoco 93 octane gasses (at least at the local gas stations). It may have been a case of one station "diluting" their gas, or it may have been attributable to the energy density in the different brands, since the turbo would make it more sensitive to how much energy was produced.

By the way, I mention that I use 93 octane, even though Mazda suggests 91. It's not that I think I'll get better performance, but rather that only Sunoco offers 91 octane in my area (they used to offer 87,89,93, and 94, now they offer 87,89,91, and 93), and I've had a few tanks of gas from them, at 91 and 93, that just didn't run well. I suspect they either sell 87 for all grades or the tanks are fouled, so I tend to avoid them, unless I'm out of town.

red22

Cheap *** People 91 Octane Why Buy A Sport Car And Put 87 In It Come On 91 Is Cleaner And Better For Your Car That Why You Pay A Little More..... And When You Bought Your Car Did The Dealer Tell You This Car Takes 91 Octane??????????????????????????????? And On The Fuel Cap It Says 91 Octane Close This Damn Thread Please.....

Outlaws eXtreme

red22, this is a Discussion forum, people will want to discuss this issue. Nothing wrong with that. Just because something says they recommend using 91, doesn't mean you MUST use 91.

Btw, interesting way of typing a sentence...

Psylence

Hey red22, why are you posting in a forum about your parents car?

icyur2

Umm..red22, I'm not that knowledgable in the car department, but from what I have read in this forum, 87 octane is CLEANER than 91. The only difference is more additives added in them and the burn rate. 91 burns slower, so it leaves more carbon crap, which is why Shell and many others out there add EXTRA additives to "clean" up the mess.

As for why people choose to put 87 vs. 91..that is their call. So chill!! I'm doing it out of curiosity after reading so many threads on performance/mileage, etc...I don't think it will affect my car any because like many thread pointed out, these babies have "knock sensors" so the chances of doing serious damages to your car is very slim. Again, that is my choice, so respect it!

On another note, so far, no affect to change in gas. I am noticing more response on the go, but have yet to eat up my tank to find out how much I'm getting per gallon. I was getting 20 miles/gallon with 91..so..am hoping I'll get 21 or 22 with 87..then again, who knows?? Either way, I'll be saving about $150/yr if this still gives me 20 miles/gallon ^_^

Psylence

Also, remember that the combustion chamber shape in a rotary engine is long and thin. Therefore, a fuel that burns FASTER is a better idea than a slow burning fuel. High octane is slower burning, as this is what prevents "knock." And since higher octane burns slower, it is mroe likely to leave carbon buildup... which is why they put shitloads of additives and detergents into "premium" fuel. It needs it.

Even my old man, a rotary hater, knew that lower octane was best for wankels. Wish he had clued me in before I pissed company loot down the rathole on high test.

And I used to put in Sunoco GT100 in my Subaru STi V.. glad those days are over!

TownDrunk

I've never tried 87. I've always used 91. I just can't justify the risk of breaking something to save $2.50/tank on average. For those of you who tried 87 and get better mileage and more power: Sweet! For me, peace of mind is worth the $2.50/tank.

icyur2

EXACTLY, TownDrunk! Every user can take this the way they want to. For you, you have the peace of mind when you are using the recommended octane. However, as the Mazda's owner's manual pointed out, you can use 87 octane. It isn't recommended, because it would "lower" the performance. Nowhere on the manual did it say DO NOT use anything BUT 91 octane. So, for me, I'm willing to save some extra $$ if the performance difference isn't substantial. Based on the many threads I've read, the RX-8 loves either one (some more so than others). That is the beauty of this car, it doesn't care if you throw in regular when it is suggested you use "premium." Others out there that says you have to use premium..well..they now are paying for it Granted, there are some RX-8 owners out there that for some bizarre reason can't even use 87...why...I don't know...every batch different I guess..and I'm lucky enough to have one that doesn't mind drinking regular...

Ole Spiff

I've been using 87 for almost 2 years; nothing is broken, car runs great. To each his own; some 8's just do not like 87 for whatever reason. Mine does; money "savings" aside. However with gas prices in the south climbing above $6 per gallon for premium now that the aftermath of the disaster is in full swing, any savings can make a difference. Today I gassed up and it was $2.93 per gallon for 87 regular; $3.13 for 91. As for "peace of mind" suit yourself. If it would 'break' the car Mazda would have put an appropriate warning in the manual and on a sticker inside the gas filler door to NOT use any grade less than premium. It just says "recommended for best performance". Since my particular car feels better with 87 I'm using 87.

Somebody else mentioned they make enough money to 'afford' premium...so do I. I paid my car off a few months after buying it so money isn't an issue; I can afford premium. However I see no reason to throw money away on something that actually lessens the responsiveness of my car just because other's aren't 'comfortable' using 87. To each his own which is why I posted this thread. IF your car likes it the way mine does, then use it, save money which you can spend on extra things for your car (the savings I've realized just in the last 2 years paid for my RB CAI) or spend however you wish. If you're not comfortable with the idea of using anything less than premium and you can 'afford' to buy premium; buy and use it.

As an aside to the octane issue, today I replaced the transmission fluid with Royal Purple and man was I surprised! I was expecting the trans to shift smoother based on what I'd read from others (which it does slightly) but I was not expecting the difference in sound. The trans is so much quieter now it's amazing. I had not realized mine was that noisy since it's always been that way from the day I got it. What a difference now! I'm going to get more of the stuff and put it in the differential now. Great oil!

rxeightr

I did the Redline option with my tranny & differential many thousand miles ago.

You will enjoy the change. And darn glad my RX-8 loves using 87 too, especially how the prices are going now.

Vertigo-1

iTrader: (3)

Well I finally decided to try a tank of Shell 87. So far so good...definitely no problems at all with normal everyday driving, and it's been quite hot this week where I live. I've been able to regularly run it to 5000 RPMs without hearing any pinging and whatnot even during a hot day. I am being a little more cautious though about going WOT to redline, those I only attempt at night when things have cooled down, no problems there either.

The only performance difference I feel is that there's less "boost" after 4000 RPMs, where the secondary intake tract opens up (I have the AT) for the rotary engine's version of VTEC . The entire power band feels truly linear and flat now, whereas with premium there was a noticeable extra surge forward when that secondary intake tract opened up.

I'm definitely going to continue using regular though now that I've determined at the very least that the car won't be pinging and knocking under regular driving conditions. Gas prices here in Hawaii is up to $3.18 for Shell premium which is the most expensive gas there is here, with it very likely going up to $3.25ish by this weekend. Regular currently is $2.98.

SDB

I used 93 for the first 4000 miles in my 05. Then I switched to 89 and I couldn't feel any difference. Mileage remained the same. at about 6000 miles I switched to 87 and still didn't feel any difference or get any different mileage, always around 18.

I did switch to 93 octane for a Sebring track event just in case at around 9000 miles. I still didn't see any difference so why bother wasting the money.

automaton

I just got done running a tank of 87 octane for posterity's sake.

I found what seems to be a 2 mpg difference in gas mileage (better gas mileage). I'm testing again with 93 to verify, but there seems to be no difference in initial roll-on acceleration, but it seems slightly "anemic" in the top end. On highway runs and passing on rural two-lane roads, there doesn't seem to be that endless rush, like the car could just keep going past the redline. The power seems to taper off beyond about 7000-7500 rpms with the 87.

I'm running another tank of 93 and I'm paying particularly close attention to the top end this time, then I'll try a couple tanks of 87 to let the computer sort everything out and see if my current observations are correct, on my particular car, anyway.

Fanman

That is your engine adjusting for the lower octane fuel, and retarding the timing of your engine. Most engines down pull out timing on the top end, but in this case the engine detects the lower grade fuel & pulls out even more timing. Getting less power on high end. In normal everyday driving you won't sense this, but when you gun it, it will become more noticeable.

Ole Spiff

If "gunning" it starts to be measured in dollars per minute that may not be the big issue soon. I remember the so-called "gas shortage" of the early 70's and what a pain it was dealing with that. If the oil industry decides they just want to brute force us into coughing up more money like they did then (there was no shortage in reality) then we can expect it again. The price gouging will be just as bad except on a much higher level. Back then gas went from 30 cents a gallon to 45 cents which sounds like nothing now, but that was a 50% increase and at the wage levels then was a big hit on the wallet.

It sounds very much like "they're doing it again" with talks of gas prices climbing above $4 which gets close to that 50% increase the oil industry loves to bump things by. If they start a phony "shortage" then the price difference between regular and premium will jump; those who have no choice but HAVE to run premium are going to get gouged the worst. If your car can run 87 now's the time to find out and make sure so that when you have to get in a long line of angry, frustrated and short-tempered people at the gas station and after an hour or more you finally get to the pump, you will have the lucky option of being able to put any available grade in your car. You have no idea how angry customers get when they've waited over an hour, get to the pump and the station is out of premium... "sorry we only have regular". Back then people actually got into fights, some even pulling guns. It never occurred to them to walk up to the station and check first, nor did it occur initially to the station owners to post big signs you could see a block away that said which grades of gas they had available.

We had the "odd/even" system going here in California then; if your license plate ended in an even number, you could get gas on Monday, Wednesday, Friday; if your plate ended on an odd number, you could buy gas on Tuesday, Thursday, Saturday....everybody could get gas on Sunday if you could find any place open. If you traveled, well the price took dramatic jumps on the open road. Instead of $0.45 per gallon like it was in the main cities, it was $1.00 per gallon, and in the remote stretches it would be as high as $1.50. I remember driving from Las Vegas to Salt Lake City during that time and there was only one station open the entire way in St. George. The lines were a block long each way. I pulled up to the line (thought there was an accident since people were standing around outside of their cars). I got out and asked what had happened and they told me "gas line". I couldn't believe it but since I was sitting on empty I had no choice but to park my car in the line and wait. I was driving a 68 Triumph Spitfire which got about 35 mpg at that time so I was lucky. I had just come all the way from Vegas so I took the opportunity to stretch my legs and walked up to the station to use the restroom (forget it; that line was ridiculous too...went "offroad" behind a tree). Price on the sign? $1.50 per gallon for premium. I was prepared for $0.50 a gallon like I had paid in Vegas; this was a huge hit on my funds. Luckily I had a $20 bill in my pocket; it was cash only, no charge cards or checks and you were limited to 10 gallons. Fortunately my car only took 10 gallons so I could fill up for the grand sum of $15. There were a lot of angry people who needed more than 10 gallons...American cars in those days were gas guzzlers and had huge tanks. I was glad they didn't run out of premium before I got to the pump. When I got closer and was talking to the others coming down from Salt Lake City, I found out they were saying this was the first station they had found open; I told them I'd just come from Vegas and this was the first station I had found open. It was the only station open the entire way. There were a lot of unhappy people in that small town that night; no place to stay, no restaurants open...just this one small station with a couple of pumps and an owner making a fortune.

If they do the phony shortage thing again, and prices at the pump hit $6 per gallon, you can imagine what all those drivers with those huge trucks and SUV's are going to be like. They tend to drive with their egos as it is, they'll be shoving and trying to force their way to the pumps cause they NEED 20 gallons of premium. It won't matter if there's a 10 gallon limit, they'll take what they want anyways. If the pumps are metered so they only pump 10 gallons, I have no doubt violence will break out. It did back then and people are far less civil now than they were then. We RX8 owners will be fortunate in that we can run any octane, so we can avoid the fights for whatever grade is missing that others HAVE to have.

Ole Spiff

Well after running a couple weeks now with the RB CAI I noticed 2 things; it leans out my A/F ratio. There is definitely less soot on the exhaust tips. I've also experienced twice under high outside temps (around 100+) with the A/C on a kind of chattering noise and sudden lessening of power when running 87 octane; I've now switched up to 89 and so far so good. The only thing that's changed is the addition of the CAI so I assume that's leaned out the mixture enough that I needed to use the higher octane now. I also noticed with 87 that I was getting about 1 mpg less mileage than I was before adding the CAI. I'm running tests with 89 to see what I get with that; I filled up today with a complete tank after a partial tank of 87 & 89.

Anybody else with the CAI experience a drop in gas mileage?

Fanman

May very well be detonation. At that point your car has retrded timing as much as it can, and can't go further. When I had a bad map on my Greddy EManage when I first put my turbo on my car, and was dynoing it at RPM I got what sounded like ball bearings in my engine, my mechanic flipped out & we turned the car off immediately. Found out it was a bad fuel map on my Emanage, got it re-flashed at Greddy. But if I had let my engine run like that it would have destroyed it in short order. Your engine is sensing detonation, and lowering timing as much as it can (loss of power), but it can't go any further, so you are getting detonation.