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What is the lowest octane an RX8 can safely use?

Old 09-11-2012, 01:01 PM
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Originally Posted by Cornbred View Post
I think htis is how the zombie apacalypse starts ... reviving from the dead posts from 1.5 years ago
You're proof that zombies exist. That was a brainless comment that offered no value, wastes people's time, all the while looking like a valid reply.
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Old 09-11-2012, 01:22 PM
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OK ill give you a reply, this isnt a prius, it is infact an expensive car to operate in comparison to other vehicles on the road, if 7 cents is that much of an issue for you perhapse this isnt the car for you. If you need conformation that -7 cents is actualy cheeper, a visit to your local elemetary school would be more of more value to you than someone saying yes .. its 7 cents cheaper, as oposed to asking that question here making people think there may actualy be valubale information or a question that someone with knowledge of the vehicle may need to answer instead of opening up pre installed calculator on your computer and doing it yourself, i a zombie? perhapse, but i can do simple math without a pat on the head confirming weather or not i did it correctly
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Old 09-11-2012, 01:39 PM
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cornbred. you have a lot to learn around here. You seem to be the angry one. I just called you a newb because you are, and now you're buthurt. Prince searched and found a relavent thread and posted in it. That's the way to do it.

Before you spout off again, I'd imagine prince here is asking if it's ok to do, not if it is cheaper. I gave him the answer "It's probably not worth the effort." You're going and bashing him and getting butthurt because you're obviously too hot headed to read the question or my response.

so, stop being a newb with an attitude, take the time to read what your posting a response to, and respond accordingly. Or you can stay an unproductive newb that is constantly butthurt.


back on topic. Prince. You'll be fine to mix it if you think it's worth the effort as long as you don't get any pinging from the lower octane fuel (wich is unlikely)
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Old 09-11-2012, 01:50 PM
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well if he was wondering if its ok to do id tell him to reference previous posts that are in this thread so he could realize and learn from the already supplied information in this post that most people wont have aproblem running lower octane fuel, however if you are in an arid or hot environment you may experience problems running lower octane fuels, the only way to really know of course is to try it, but you dont need forums for that, pretty sure its in the manual.
Time for a drive, you gentalmen have a good day
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Old 09-11-2012, 01:58 PM
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Originally Posted by Cornbred View Post
well if he was wondering if its ok to do id tell him to reference previous posts that are in this thread so he could realize and learn from the already supplied information in this post

Exactly my point of why it was better for him to bump this thread.


someone is totally

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Old 09-11-2012, 02:23 PM
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Cornbred? More like inbred....
Yeah, go pick up your sister-mom-cousin for your date. And don't worry about mileage because you're good at math and you can afford the extra 7 cents for your fancy brilliant black. That's why you're driving an '06? Idiot.
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Old 09-11-2012, 02:28 PM
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Prince.

No need for that **** either. Newb on newb fighting is pointless.
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Old 09-13-2012, 12:29 AM
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Cornbread really? Read and follow the Manuel? Well I guess your the one keepin the mechanics at the dealer working. I know the Manuel says if you have issues see the dealer ASAP. And to take it in for service every some many miles don't add fuel additives or anything else. Idn about anyone else but I use additives, change my own oil, use Syncromesh in my 6spd, use synthetic gear fluid in the diff, etc... But I guess the dealer knows everything. I'm not sayin they don't do research cause they do but they have to make he manuel that works for everyone from Alaska to the desert here in SoCal. There are things here that make the. At run better that make it run like **** other places and the other way around. As far as runnin 87 I only run it here in the winter when highs are 80's instead of 118+. And then I run 91 with lucas fuel stabilizer rebuilt my motor 10k ago and it was clean as a whistle with over 100k on it. Same with the trans. Gears were worn but not much. The only way is to try a few tanks and carry a brand name octane booster. But do your research. Most "boosters" only raise the octane by .5-.8 due to government regs. Just like fuel cleaner. The best stuff that works you can't buy on the shelf. 3M makes a fuel cleaner/decarbonizer that works wonders but I don't think the normal consumer can touch it.
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Old 09-27-2012, 10:44 AM
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mix 94 with 87

3rd tank with the mix, no knocking, pinging, sputtering, or rough idle.
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Old 09-28-2012, 01:30 AM
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Oh man I love reading through the threads on this forum lol Always entertaining. I myself have never understood the whole gas price dillema that people get struck with. My friends and family will say things like "gas is $x.xx a gallon omg" But honestly you're going to pay for it no matter what and the $3.73 cents you paid for 85 today instead of a 30 cent difference for premium is not going to matter when you pay$3.93 a few weeks later for that same 85 :-P Gas prices will be gas prices just pump it.
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Old 10-01-2012, 02:12 PM
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Jesus... here in NY im paying $4.25 for 93. Ridiculous.

I got my car with 14K miles on it and now im at 55K. Ive been using nothing but 93 (sometimes it was mixed due to certain gas stations not having anything higher than 89). I almost always used Shell V-Power with the exception being the last 10K miles where i would sometimes use Gulf 93 because they were 30 cents cheaper a gallon.

I use 93 for 2 reasons. I always figured that since this engine runs 2.5 times hotter than piston engines, and revs to 9K... higher octane would most definitely help against pre-ignition. The other reason was because i want this engine to last and dont want carbon buildup so i usually use V-Power since they have a **** ton of detergents.

Runs fine for me. I guess i could try out Shell 89 (wish they had 91 somewhere by me). If it nets me more gas mileage id be happy. Shell always has more detergents than most so im fine with that.
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Old 10-01-2012, 04:32 PM
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89 for winter/cooler months and a mix of 89 and 93 for summer/warmer months works fine for me.
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Old 10-09-2012, 10:06 AM
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So, back on topic, how would premixing affect the car if you are running 87 octane? Do you need to run 91-93 if you premix? This may have been covered, but I haven't been able to find it.
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Old 10-09-2012, 01:05 PM
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Well if you fill up with 15 gallons of fuel you have nearly 2000 fluid ounces in there and most people add a half ounce of premix per gallon. So 7.5 ounces to almost 2000 ounces, I don't think there is going to be a significant change there.

You should still be using premium IMO.
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Old 12-11-2018, 10:42 PM
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This make sense ? From another source
The lower the octane the faster and more volatile the burn. The rotary has a very short combustion area and the Renny is worse since it is a zero overlap engine. The faster the burn the more complete the burn and the more power you will make. Ignition system is irrelevant beyond it needs to be in working order.
On 100 octane we made 218whp, on 91 we made 224, on 87 we made 228/230. Fuel being the only difference in that testing. Unfortunately most racing organizations require a specific fuel to be used and do fuel testing, so we were usually not able to run 87oct except in Club racing.
Premix has no bearing since we used the same premix in the same ratio across all octane ratings.

Last edited by Sydo; 12-11-2018 at 11:02 PM.
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Old 12-12-2018, 10:10 AM
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All the way back to 2012 in the RX-8 time machine eh?

I took my car to Hallett Raceway last November, where they only had 87 available and it ran fine with 1oz per gallon of premix for 4 days, although the ECU retarded the timing, causing it to be slightly down on power. So, it just took a little longer to reach 88mph, but it still got there.
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Old 12-12-2018, 10:29 AM
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I don't buy the "volatile burn" having a causal relationship with HP for a number a reasons, no least of which are wheel dyno numbers are pretty damned unreliable there's no source for your quote.
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Old 12-12-2018, 11:49 AM
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Old 12-12-2018, 03:00 PM
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Originally Posted by Sydo View Post
This make sense ? From another source
The lower the octane the faster and more volatile the burn. The rotary has a very short combustion area and the Renny is worse since it is a zero overlap engine. The faster the burn the more complete the burn and the more power you will make. Ignition system is irrelevant beyond it needs to be in working order.
On 100 octane we made 218whp, on 91 we made 224, on 87 we made 228/230. Fuel being the only difference in that testing. Unfortunately most racing organizations require a specific fuel to be used and do fuel testing, so we were usually not able to run 87oct except in Club racing.
Premix has no bearing since we used the same premix in the same ratio across all octane ratings.
If you look at the meaning of AKI, it means Anti-Knock Index.

A lower octane fuel is more prone to knocking, where the fuel gets ignited before you want it to. Knocking is very bad for the engine.

RX-8, like most cars, come with knock sensors. When these sensors pick up anything, they will make the ECU retard the timing to protect the engine. The spark plugs fire a bit later than usual and you actually lose power.
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Old 12-17-2018, 10:08 PM
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After driving seven rotary engine cars easily a total of over a million miles since 1972 on street and track, anyone who thinks they can safely run low octane gas in their rotary engine longterm ,deserves the knocking,ultimate shortened life and poorer performance they get.

Last edited by gwilliams6; 12-17-2018 at 10:40 PM.
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Old 12-17-2018, 10:11 PM
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Quote was from a Don Walker
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Old 12-17-2018, 10:54 PM
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The more I look at it, the less sense it makes...

First of all, as long as they have the same amount of ethanol, a high octane fuel and a low octane fuel should have the same energy content. They both should release almost the same amount of energy when ignited properly.

Secondly, the reason high octane helps with power is that you can compress it more before the spark plug has to fire. A lower octane will have to be ignited sooner so it doesn't knock. Higher compression = more power.

So yeah, I'd like to see a dyno graph or video.

Originally Posted by gwilliams6 View Post
After driving seven rotary engine cars easily a total of over a million miles since 1972 on street and track, anyone who thinks they can safely run low octane gas in their rotary engine longterm ,deserves the knocking,ultimate shortened life and poorer performance they get.
Less performance, sure, but shortened life? I don't think so unless you live in a very hot area with low humidity.

As mentioned, the 8 comes with knock sensors. They will pull the timing to prevent the engine from knocking.

Can't bring older rotaries cars into the conversation unless they are naturally aspirated and have knock sensors.
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Old 12-18-2018, 05:36 AM
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Premix while changing octane

i have done this before and have experienced reduction of power and mileage, from 93 to 87 then to 91 and have concluded 91 works best even with premix
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Old 12-19-2018, 09:21 AM
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Originally Posted by UnknownJinX View Post
The more I look at it, the less sense it makes...

First of all, as long as they have the same amount of ethanol, a high octane fuel and a low octane fuel should have the same energy content. They both should release almost the same amount of energy when ignited properly.

Secondly, the reason high octane helps with power is that you can compress it more before the spark plug has to fire. A lower octane will have to be ignited sooner so it doesn't knock. Higher compression = more power.

So yeah, I'd like to see a dyno graph or video.



Less performance, sure, but shortened life? I don't think so unless you live in a very hot area with low humidity.

As mentioned, the 8 comes with knock sensors. They will pull the timing to prevent the engine from knocking.

Can't bring older rotaries cars into the conversation unless they are naturally aspirated and have knock sensors.
No one has any figures on the longevity of Renesis engines using lower octane fuel. But in my experience with NA and Boosted rotaries over 46 years I have seen more rapid wear (internally on teardown) with engines that ran on lower octane. Just my own experiences, your's may be much different. This is nothing new, folks trying to save money running lower octane than recommended in their rotary engines. I never did in all those 46 years and never had a rotary engine failure, ever. The only engine replacement I did was on my 2008 40th Anniversay Edition RX8 when it tested for borderline low compression numbers just one month before the eight-year warranty was up in 2016, and my dealer approved a reman engine for me. It still ran fine, but getting a reman from Mazda under the warranty was a no-brainer. Cheers

Last edited by gwilliams6; 12-19-2018 at 09:29 AM.
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Old 12-27-2018, 09:48 PM
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Originally Posted by gwilliams6 View Post
After driving seven rotary engine cars easily a total of over a million miles since 1972 on street and track, anyone who thinks they can safely run low octane gas in their rotary engine longterm ,deserves the knocking,ultimate shortened life and poorer performance they get.
and how good where the knock sensors before 2004?

i will say as at 140k miles on 87 street and 93 on track it has been all good.. note, if under cruise on the interstate 87 gets the nod for mileage.

beers
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