premium unleaded ?
04-09-2008, 10:58 AM
#51
Can ANYONE here tell me WHY I should use premium other than your butt dyno or your brother's uncle told you to or your friends xyz car does better with it?
I have driven rotaries for more than 15 years, RX-3's, and 7's in both 1st gen and 2nd gen guise. There are 2 race-prepped 7's in my garage (SCCA road racing) and a new to me, used RX-8 in my carport. I have always used 87 octane in my street cars with no ill results whatsoever. Has anyone stopped to think about what the OMP does? Have you stopped to think why your rotary actually USES oil. It injects it into the rotor housing where it is mixed with the fuel during combustion. Doesn't the oil lower the octane rating of the fuel?
We actually use pre-mix in all of our race engines with 87 octane. Jim downing reccomended 87 with pre-mix. These engines are as close to a 2 cycle engine as they are a 4 cycle.
I will freely admit the RX-8 is new to me but I have a lot of experience with rotaries. So what's SO different in this engine to force me into using premium. It's not a matter of money, my M5 required premium, my turbo Volvo requires premium but my rotaries don't. Someone with some more experience then me please chime in and help me out.
I have driven rotaries for more than 15 years, RX-3's, and 7's in both 1st gen and 2nd gen guise. There are 2 race-prepped 7's in my garage (SCCA road racing) and a new to me, used RX-8 in my carport. I have always used 87 octane in my street cars with no ill results whatsoever. Has anyone stopped to think about what the OMP does? Have you stopped to think why your rotary actually USES oil. It injects it into the rotor housing where it is mixed with the fuel during combustion. Doesn't the oil lower the octane rating of the fuel?
We actually use pre-mix in all of our race engines with 87 octane. Jim downing reccomended 87 with pre-mix. These engines are as close to a 2 cycle engine as they are a 4 cycle.
I will freely admit the RX-8 is new to me but I have a lot of experience with rotaries. So what's SO different in this engine to force me into using premium. It's not a matter of money, my M5 required premium, my turbo Volvo requires premium but my rotaries don't. Someone with some more experience then me please chime in and help me out.
04-09-2008, 01:43 PM
#52
04-09-2008, 01:51 PM
#53
04-09-2008, 02:23 PM
#55
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So still no one can site any reason other than Mazda says so. I'm not suggesting that's a bad reason, but WHY does Mazda say so?
I am quite familiar with the new Renesis motor, I understand it has higher compression than the previous engines. I know all about the side ports vs. the peripheral ports. I have stock engines, street ported engines, small bridge ports, large "j" bridge ports and a few racing buddies with peripheral ports. I UNDERSTAND rotary theory. I have LOST of rotor housings and end plates in the garage to practice porting on.
I still don't think most realize how this motor actually works. You need to think more in terms of a weedeater engine than the engine in your grandpappies truck.
It has always been my understanding that mixing oil with gas lowers the octane rating. Your engine does this on its own.
Am I wrong on this account?
I am quite familiar with the new Renesis motor, I understand it has higher compression than the previous engines. I know all about the side ports vs. the peripheral ports. I have stock engines, street ported engines, small bridge ports, large "j" bridge ports and a few racing buddies with peripheral ports. I UNDERSTAND rotary theory. I have LOST of rotor housings and end plates in the garage to practice porting on.
I still don't think most realize how this motor actually works. You need to think more in terms of a weedeater engine than the engine in your grandpappies truck.
It has always been my understanding that mixing oil with gas lowers the octane rating. Your engine does this on its own.
Am I wrong on this account?
04-09-2008, 02:35 PM
#56
We have similar histories. I always used regular in my race cars. The RX8 has higher compression rotors than previous engines. In the RX8, I have noticed my exhaust note changes. And some people report better gas milage, when using premium. Mazda recommends 91 octane gasoline be used.
2004 Mazda RX8 Owners Manual pg. 4-2
There are a lot of could's in that statement. I have used 87 octane successfully. I just think the PCM is pulling timing when I do and performance is reduced. Engine knock or ping will be determined by the quality of the gas you are using.
Last edited by alnielsen; 10-13-2008 at 07:32 PM.
04-09-2008, 03:02 PM
#57
Huge hole is huge
Everybody uses whatever fuel they want, either because they believe it's better for the engine/wallet/whatever. Me? I use 91, because it gives me piece of mind.
04-09-2008, 04:02 PM
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04-09-2008, 04:33 PM
#59
I did read it and this is why I scanned it. Only 91 in my car or better. I do not want to hinder the performance of my car in any way shape or form... 
I financed not leased so this should help understand a bit better. I plan on keeping my car not letting it go in a few years... So over a period of time I do believe that using 87 will eventually damage my engine.
I financed not leased so this should help understand a bit better. I plan on keeping my car not letting it go in a few years...
So over a period of time I do believe that using 87 will eventually damage my engine.
04-09-2008, 04:52 PM
#60
Your car must be a later model then the 05 because my 05 manual states that 87 can be used but you may experience reduced performance. There is no mention of high temperature and low humidity in the 05 manual. I have also not received anything from Mazda correcting this statement in may manual.
The wording in your manual is interesting, Mazda is obviously covering there *** here. A few users have reported knocking with lower octane, some have reported knocking with high octane so it is pretty obvious that some RX-8 have a problem which will cause knocking. It is easier(cheaper) for Mazda to throw a blank statement of "use high octane" rather then addressing the problem in these cars.
I will stand by my original statement that if your not experiencing any knocking stick with 87. I to bought my car and plan to keep it for a while and I feel very comfortable with this practice.
The wording in your manual is interesting, Mazda is obviously covering there *** here. A few users have reported knocking with lower octane, some have reported knocking with high octane so it is pretty obvious that some RX-8 have a problem which will cause knocking. It is easier(cheaper) for Mazda to throw a blank statement of "use high octane" rather then addressing the problem in these cars.
I will stand by my original statement that if your not experiencing any knocking stick with 87. I to bought my car and plan to keep it for a while and I feel very comfortable with this practice.
Last edited by Raptor75; 04-09-2008 at 05:04 PM.
04-09-2008, 05:19 PM
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Thanks fo the info alnielson. Sometimes I forget there is more speculation than actual fact on these forums.
Still looking for solid answers. If anyone has any good info to share I's like to hear it.
Still looking for solid answers. If anyone has any good info to share I's like to hear it.
04-09-2008, 08:34 PM
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Ive take this on another forum hope it will help. ( May not apply to rotary engine)
I'm not sure what kind of expert opinion you are looking for. But if you are running 93 octane, you ARE losing power, and you ARE going to build up crap and contaminants in your engine much quicker. They always say 87 or higher, because of the fact that some places may only offer 88 or 89.
You are wasting money, you are losing power, and you are gonna have a fairly gunked up engine by the time you get up there in mileage.
I'll explain this again since you seemed to have missed the technical explinations. The only thing octane rating is, is resistance to detonation and heat. The higher the octane, the more heat required to get the mixture to ignite.
Hence the reason cars with higher compression engine or turbos require premium. Cars with turbos, etc, and with higher compression tend to have their mixture get much hotter in the combustion chamber before the ignition spark. Using a lower octane gas in a car that requires premium causes premature detonation (which is bad, duh) since the heat detonates the lower octane gas.
Likewise, if you are using higher octane gas in your civic, the mixture may not get hot enough in your combustion chamber to burn completely through. This leaves excess fuel/air mixture in your combustion chamber during the exhaust stroke, causing a loss of power and buildup of excess contaminants. Stop using 93 octane, because you're losing power and you're pissing money away. This also burns your valves and over time you will burn through them.
As for using high octane gas and nitrous, this is somewhat a paradoxical situation. Nitrous can benefit from using higher octane gas, since the oxidization process induced by nitrous causes the mixture to super heat. again higher octane gas is more resistant to heat, therefore will help prevent detonation when spraying.
however, when you're not spraying, you're back into the category above, where it's causing loss of power and excess waste and contaminants.
As for using 100 octane gas in your car, I'd advise against that in a very cautious sense. The addatives in higher octane gas worsens the effect you're seeing here, even if you're using nitrous. Turbos can use it if they crank up their boost to the point that they'd benefit from it. However, most don't do that unless they've been tuned for it, becuase running high octane gas and high boost without being tuned is a very dangerous combination to gamble with.
If you see some ricer in his n/a civic filling up with 100 octane, point and laugh, because everyone else who actually knows what they are doing, will certainly be laughing along with you.
Oh and I found out the thing with the injectors. The addative that they use to give gas its higher octane can cause premature injector failure, injector misfires, etc, if your injectors were not made for that kind of fuel. This is an extreme case and few and far between, but it can happen, and does happen. I have to go back and look, but the addatives cause buildup on the injectors, leading to the above said failures. However, this is not always the case, so really, it's hardly worth mentioning.
------------
This is SCIENTIFIC FACT! Methanol is completely different than using pump gas. You can't even compare the two.
No, higher octane gas does not burn more cleaner, nor does it burn more completely.
ALL THE OCTANE RATING MEANS IS THAT IT IS MORE RESISTANT TO DETONATION AND HEAT!!!
And as for the person who got better mileage with 89 than 87. Assuming your car isn't FI'd then you did NOT get better mileage just because you used higher octane. There are too many other factors involved to do an experiment like that. The ONLY case where this would be is if your car was detonating for some reason, but you'd get a CEL if something was that majorly wrong.
Also, the whole "well premium gas has more cleaners in it to help your car". wrong. government regulations prevent this. the only difference is the addative used to increase octane rating.
Once again. Higher octane gas is more resistant to heat and detonation. (this also means it takes longer to burn, which is WHY if you DONT have a car set up for premium you'll eventually burn through your valves). If you are going to run premium you have to tune for premium. you would have to advance your timing 2 degrees and retard your exhaust valves in order to allow the mixture to burn through completely before the scavaging of the chamber.
---------
Here... so you know I'm not talking just "hearsay"
this was in a pdf i found at the american petroleum institute. here are some excerpts. i believe this was also hilighted on the service advisor web site.
WHAT IS OCTANE RATING?
Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions.
I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK?
It did in older engines using carburetors to regulate air/gas mix They cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution.
However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.
Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only.
WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?
You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.
DOESN'T HIGHER OCTANE GASOLINE HAVE MORE CLEANING ADDITIVES THAT ARE GOOD FOR MY ENGINE?
No. Government regulations require that all gasoline contain basically the same amount of additives to clean the injectors and valves. The only differences are the type to help create the different octane ratings. All gasoline burns at the same rate, it is the additives that create the different octane ratings for the different types of engines.
http://auto.howstuffworks.com/question90.htm
And here's from the federal trade commission.
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm
I'm not sure what kind of expert opinion you are looking for. But if you are running 93 octane, you ARE losing power, and you ARE going to build up crap and contaminants in your engine much quicker. They always say 87 or higher, because of the fact that some places may only offer 88 or 89.
You are wasting money, you are losing power, and you are gonna have a fairly gunked up engine by the time you get up there in mileage.
I'll explain this again since you seemed to have missed the technical explinations. The only thing octane rating is, is resistance to detonation and heat. The higher the octane, the more heat required to get the mixture to ignite.
Hence the reason cars with higher compression engine or turbos require premium. Cars with turbos, etc, and with higher compression tend to have their mixture get much hotter in the combustion chamber before the ignition spark. Using a lower octane gas in a car that requires premium causes premature detonation (which is bad, duh) since the heat detonates the lower octane gas.
Likewise, if you are using higher octane gas in your civic, the mixture may not get hot enough in your combustion chamber to burn completely through. This leaves excess fuel/air mixture in your combustion chamber during the exhaust stroke, causing a loss of power and buildup of excess contaminants. Stop using 93 octane, because you're losing power and you're pissing money away. This also burns your valves and over time you will burn through them.
As for using high octane gas and nitrous, this is somewhat a paradoxical situation. Nitrous can benefit from using higher octane gas, since the oxidization process induced by nitrous causes the mixture to super heat. again higher octane gas is more resistant to heat, therefore will help prevent detonation when spraying.
however, when you're not spraying, you're back into the category above, where it's causing loss of power and excess waste and contaminants.
As for using 100 octane gas in your car, I'd advise against that in a very cautious sense. The addatives in higher octane gas worsens the effect you're seeing here, even if you're using nitrous. Turbos can use it if they crank up their boost to the point that they'd benefit from it. However, most don't do that unless they've been tuned for it, becuase running high octane gas and high boost without being tuned is a very dangerous combination to gamble with.
If you see some ricer in his n/a civic filling up with 100 octane, point and laugh, because everyone else who actually knows what they are doing, will certainly be laughing along with you.
Oh and I found out the thing with the injectors. The addative that they use to give gas its higher octane can cause premature injector failure, injector misfires, etc, if your injectors were not made for that kind of fuel. This is an extreme case and few and far between, but it can happen, and does happen. I have to go back and look, but the addatives cause buildup on the injectors, leading to the above said failures. However, this is not always the case, so really, it's hardly worth mentioning.
------------
This is SCIENTIFIC FACT! Methanol is completely different than using pump gas. You can't even compare the two.
No, higher octane gas does not burn more cleaner, nor does it burn more completely.
ALL THE OCTANE RATING MEANS IS THAT IT IS MORE RESISTANT TO DETONATION AND HEAT!!!
And as for the person who got better mileage with 89 than 87. Assuming your car isn't FI'd then you did NOT get better mileage just because you used higher octane. There are too many other factors involved to do an experiment like that. The ONLY case where this would be is if your car was detonating for some reason, but you'd get a CEL if something was that majorly wrong.
Also, the whole "well premium gas has more cleaners in it to help your car". wrong. government regulations prevent this. the only difference is the addative used to increase octane rating.
Once again. Higher octane gas is more resistant to heat and detonation. (this also means it takes longer to burn, which is WHY if you DONT have a car set up for premium you'll eventually burn through your valves). If you are going to run premium you have to tune for premium. you would have to advance your timing 2 degrees and retard your exhaust valves in order to allow the mixture to burn through completely before the scavaging of the chamber.
---------
Here... so you know I'm not talking just "hearsay"
this was in a pdf i found at the american petroleum institute. here are some excerpts. i believe this was also hilighted on the service advisor web site.
WHAT IS OCTANE RATING?
Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions.
I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK?
It did in older engines using carburetors to regulate air/gas mix They cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution.
However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.
Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only.
WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?
You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.
DOESN'T HIGHER OCTANE GASOLINE HAVE MORE CLEANING ADDITIVES THAT ARE GOOD FOR MY ENGINE?
No. Government regulations require that all gasoline contain basically the same amount of additives to clean the injectors and valves. The only differences are the type to help create the different octane ratings. All gasoline burns at the same rate, it is the additives that create the different octane ratings for the different types of engines.
http://auto.howstuffworks.com/question90.htm
And here's from the federal trade commission.
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm
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