Octane requirements
#27
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Originally Posted by PoorCollegeKid
However, if you like spinning it up to redline and feeling it push you back in your seat, or if you're towing something with your '8 or traveling through hilly areas, you really should use the minimum recommended octane (91, IIRC).
Now that is a violation of the manual.
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Originally Posted by quack_p
Towing something? What might you be towing?
Now that is a violation of the manual.
Now that is a violation of the manual.
Haha, I guess that would be :p
Originally Posted by Grabitquick
Then again, regardless of where I happen to be driving, I often wonder if the octane I'm supposed to be getting is what I'm really paying for. Depends on the Department of Weights and Measures (or the equivalent agency) in the place I'm in.
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Originally Posted by Fanman
93 octane is fine. The way the ECU work in the US is that it functions optimally at 91 octane because in many states that is the best you can get, unless you spend $5/gal and get race fuel at limited gas stations. So while the ECU can sense lower octane and retard the timing (lower hp in the process), it won't advance the timing when you 93 octane. The 91 octane map is the best it is going to get for our cars from the factory. Some aftermarket companies have made 93 octane maps for other car brands. For example the Porsche aftermarket tuner Evo Motorsports has 93, & 91 octane maps for their 600 hp + 911 Turbo cars.
I'm just playing devil's advocate---If you follow the owner's manual to the letter, the only approved octane levels are 87-91 (91-96 RON). Using 93 octane is not allowed according to the owner's manual, and I'm sure using unapproved fuel would be grounds for denying warranty service.
MazdaspeedFeras,
It's not a simple comparison of the price of the fuel. I've read a lot of posts where people claim to get much better mpg with the lower octane fuel.
#30
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Originally Posted by bowman
MazdaspeedFeras,
It's not a simple comparison of the price of the fuel. I've read a lot of posts where people claim to get much better mpg with the lower octane fuel.
It's not a simple comparison of the price of the fuel. I've read a lot of posts where people claim to get much better mpg with the lower octane fuel.
fair enough i did a cost analysis on this in another thread
Originally Posted by MazdaspeedFeras
a simple financial analysis:
average driver drives 12000 miles a year
extensive driver drives 18000 miles a year
combined worst mpg here are about 14mpg and best are about 22 mpg
the average driver with terrible mileage (using 93) will pay ~2.00 per gallon which ends up being a yearly expense of (12000/14)*2.00=$1714.29
if that average driver had great mileage he would pay (12000/22)*2.00=$1090.90
a savings of $623.39 per year for the 22mpg driver.
the 18000 driver with terrible mileage will pay (18000/14)*2.00=$2571.42 for gas
the 18000 driver with great mileage will pay (18000/22)*2.00=$1636.37 for gas
a savings of $935.06 per year for the 22mpg driver.
in both these examples the difference is 8mpg...if a modest (read: likely) increase of 2 or 4 mpg were expected then in the first example the savings go down to $156/year for 2mpg and $311.70/year for the 4mpg, and the same modest increase for the 18000 mile driver would result in a savings of $233.77 a year for 2mpg and $467.53 for 4mpg.
so what does this all mean...the benefits of driving this car like you would any economy car will result in savings of roughly 150-300 dollars ayear for the average driver ($12.50-$25 a month) and 230-470 dollars for the extensive driver ($19.16-$39.16 a month)
to me i find the sum of 40/month almost trivial, thats half the price of a nice night out...which cutting out 1 a month would be an easier prospect then not driving this car to the edge, the way it was bred to be driven. Personally i dont think the savings at the pump are enough to justify a change in driving style for me...gas just isnt that prohibitively expensive.
average driver drives 12000 miles a year
extensive driver drives 18000 miles a year
combined worst mpg here are about 14mpg and best are about 22 mpg
the average driver with terrible mileage (using 93) will pay ~2.00 per gallon which ends up being a yearly expense of (12000/14)*2.00=$1714.29
if that average driver had great mileage he would pay (12000/22)*2.00=$1090.90
a savings of $623.39 per year for the 22mpg driver.
the 18000 driver with terrible mileage will pay (18000/14)*2.00=$2571.42 for gas
the 18000 driver with great mileage will pay (18000/22)*2.00=$1636.37 for gas
a savings of $935.06 per year for the 22mpg driver.
in both these examples the difference is 8mpg...if a modest (read: likely) increase of 2 or 4 mpg were expected then in the first example the savings go down to $156/year for 2mpg and $311.70/year for the 4mpg, and the same modest increase for the 18000 mile driver would result in a savings of $233.77 a year for 2mpg and $467.53 for 4mpg.
so what does this all mean...the benefits of driving this car like you would any economy car will result in savings of roughly 150-300 dollars ayear for the average driver ($12.50-$25 a month) and 230-470 dollars for the extensive driver ($19.16-$39.16 a month)
to me i find the sum of 40/month almost trivial, thats half the price of a nice night out...which cutting out 1 a month would be an easier prospect then not driving this car to the edge, the way it was bred to be driven. Personally i dont think the savings at the pump are enough to justify a change in driving style for me...gas just isnt that prohibitively expensive.
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Great idea, although it's comparing only mpg.
12,000 miles
14mpg @ $2.01/gl---1722.86
18mpg @ $1.81/gl---1200
Difference---522.86-(43.57/month)
I freely admit that I pulled the mpg numbers out of the air.
12,000 miles
14mpg @ $2.01/gl---1722.86
18mpg @ $1.81/gl---1200
Difference---522.86-(43.57/month)
I freely admit that I pulled the mpg numbers out of the air.
#33
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#34
Yes and the writers of the FTC writeup don't own RX-8s. I truly think the owners manual is correct. 91 Oct. I asked my dealer several times when I bought the car about the octane, and everyone at different times and not with any of the others said to only use the 91 and no lower. This came from the service dept manager as well as the sales staff. Yeah I know you can't trust the sales staff but I think they are telling the truth here. My mother-in-law owns a caddy. The manual says 91 oct and she uses 87 or lower. The engine knocks too and I can't convince her she is hurting the engine. She said the salesman told them they could run on lower octs!! I would not want to risk the rotary with a lower Oct but its your car and so you can find out what is what with the Octs.
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If there's one thing my buying experience proved to me, it's that the sales staff don't know squat about the technical aspects of the RX-8. Anyone who has spent 10 minutes browsing this forum knows more about the RX-8 than the average Mazda salesman. So no, I wouldn't trust a salesman's advice on how to take care of your car. My dealer put 87 octane in the car while I was standing next to him. I told him to stop, I'll forgo the free tank of gas.
Last edited by quack_p; 10-06-2004 at 05:29 PM.
#36
Your dealer put in 87 oct in your RX? Wow! Yeah I known he sales staff don't know squat about these cars. I seen it first hand from three of them. I did believe the service manager and I only bought the car a few weeks ago so they know a little about these cars by now I hope. LOL
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Tayninh, I'm not opining on whether the FTC is right or not. I posted it only FYI. You'll get basically the same information from virtually every source you check. Bottom line is, if the engine doesn't knock or ping during normal driving with 87 octane, then you're not hurting it. If it does knock, then switch to a higher octane, but the engine still may need a tune-up at least as much as it might need premium fuel. If you use at least 87, then you're within the Mazda specs and you haven't raised any warranty issues.
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Originally Posted by quack_p
My dealer put 87 octane in the car while I was standing next to him.
#39
Well I fill up with 93 every tank..cant find 91 no such number it goes 87, 89, 92 or 93 depends on the station.. Cheaper stations like speeway have 92.. which I dont go to.. only fill up a MOBIL or Marthon, and last SHELL.
Last tank.. went 280miles on 11.435gal.. Topped it off and then went 308 miles to 12.631
Wooot.... have 11,004 miles on the car. Smooth as ever..
Last tank.. went 280miles on 11.435gal.. Topped it off and then went 308 miles to 12.631
Wooot.... have 11,004 miles on the car. Smooth as ever..
#41
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In the beginning I drove a few tanks of 91 octane, then always 87.
Never had a problem until on a road trip when I was forced to buy COSTCO gas. I took 87 Octane and I heard a pinging sound at speeds over 80 mph.
Lower speed - no ping.
Immediately filled up with 91 Chevron, no ping. After that I returned to 87 gas, but no Costco again.
Well, as I said, I was *forced* to fill Costco there. 15 miles on yellow light, at night, unknown area, no gas station in sight except that Costco one.
I don't think that good brand 87 octane rated gas damages the RX-8.
Never had a problem until on a road trip when I was forced to buy COSTCO gas. I took 87 Octane and I heard a pinging sound at speeds over 80 mph.
Lower speed - no ping.
Immediately filled up with 91 Chevron, no ping. After that I returned to 87 gas, but no Costco again.
Well, as I said, I was *forced* to fill Costco there. 15 miles on yellow light, at night, unknown area, no gas station in sight except that Costco one.
I don't think that good brand 87 octane rated gas damages the RX-8.
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Originally Posted by ptiemann
In the beginning I drove a few tanks of 91 octane, then always 87.
Never had a problem until on a road trip when I was forced to buy COSTCO gas. I took 87 Octane and I heard a pinging sound at speeds over 80 mph.
Lower speed - no ping.
Immediately filled up with 91 Chevron, no ping. After that I returned to 87 gas, but no Costco again.
Well, as I said, I was *forced* to fill Costco there. 15 miles on yellow light, at night, unknown area, no gas station in sight except that Costco one.
I don't think that good brand 87 octane rated gas damages the RX-8.
Never had a problem until on a road trip when I was forced to buy COSTCO gas. I took 87 Octane and I heard a pinging sound at speeds over 80 mph.
Lower speed - no ping.
Immediately filled up with 91 Chevron, no ping. After that I returned to 87 gas, but no Costco again.
Well, as I said, I was *forced* to fill Costco there. 15 miles on yellow light, at night, unknown area, no gas station in sight except that Costco one.
I don't think that good brand 87 octane rated gas damages the RX-8.
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@fanman:
Thanks for the explanation. That makes sense. I'd like to hear a quantification how much I lose. Because nobody here has said that yet. I personally could not feel a difference over several tank fills.
Thinking it through, I suppose I bought the car for the looks. Certainly not to race others. And I enjoy the feeling of control in curves at rather high speed. Would that be an 'extreme' situation requiring higher octane? I didn't think so.
I don't do 7000 rpm clutch drops. Maybe doing that one would get a 5.9s 0-60 run versus 6.4 or save a 0.2s on a quarter mile. I'm willing to learn though. So:
My question is: how much difference does 91 versus 87 really make? Quantify it in hp, or average difference in 0-60 or 1/4 mile runs.
I'm tired of hearing "you sacrifice hp", because I couldn't notice the difference in every-day driving. For the record, I can feel the difference between a 200 hp Firebird, a 228 hp Boxster and a 238 (?) hp RX-8.
Anyway, thanks for your good explanation but numbers please.
Thanks for the explanation. That makes sense. I'd like to hear a quantification how much I lose. Because nobody here has said that yet. I personally could not feel a difference over several tank fills.
Thinking it through, I suppose I bought the car for the looks. Certainly not to race others. And I enjoy the feeling of control in curves at rather high speed. Would that be an 'extreme' situation requiring higher octane? I didn't think so.
I don't do 7000 rpm clutch drops. Maybe doing that one would get a 5.9s 0-60 run versus 6.4 or save a 0.2s on a quarter mile. I'm willing to learn though. So:
My question is: how much difference does 91 versus 87 really make? Quantify it in hp, or average difference in 0-60 or 1/4 mile runs.
I'm tired of hearing "you sacrifice hp", because I couldn't notice the difference in every-day driving. For the record, I can feel the difference between a 200 hp Firebird, a 228 hp Boxster and a 238 (?) hp RX-8.
Anyway, thanks for your good explanation but numbers please.
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Originally Posted by ptiemann
@fanman:
Thanks for the explanation. That makes sense. I'd like to hear a quantification how much I lose. Because nobody here has said that yet. I personally could not feel a difference over several tank fills.
Thinking it through, I suppose I bought the car for the looks. Certainly not to race others. And I enjoy the feeling of control in curves at rather high speed. Would that be an 'extreme' situation requiring higher octane? I didn't think so.
I don't do 7000 rpm clutch drops. Maybe doing that one would get a 5.9s 0-60 run versus 6.4 or save a 0.2s on a quarter mile. I'm willing to learn though. So:
My question is: how much difference does 91 versus 87 really make? Quantify it in hp, or average difference in 0-60 or 1/4 mile runs.
I'm tired of hearing "you sacrifice hp", because I couldn't notice the difference in every-day driving. For the record, I can feel the difference between a 200 hp Firebird, a 228 hp Boxster and a 238 (?) hp RX-8.
Anyway, thanks for your good explanation but numbers please.
Thanks for the explanation. That makes sense. I'd like to hear a quantification how much I lose. Because nobody here has said that yet. I personally could not feel a difference over several tank fills.
Thinking it through, I suppose I bought the car for the looks. Certainly not to race others. And I enjoy the feeling of control in curves at rather high speed. Would that be an 'extreme' situation requiring higher octane? I didn't think so.
I don't do 7000 rpm clutch drops. Maybe doing that one would get a 5.9s 0-60 run versus 6.4 or save a 0.2s on a quarter mile. I'm willing to learn though. So:
My question is: how much difference does 91 versus 87 really make? Quantify it in hp, or average difference in 0-60 or 1/4 mile runs.
I'm tired of hearing "you sacrifice hp", because I couldn't notice the difference in every-day driving. For the record, I can feel the difference between a 200 hp Firebird, a 228 hp Boxster and a 238 (?) hp RX-8.
Anyway, thanks for your good explanation but numbers please.
Does that mean you are offering up your car to measure the difference ? I for one would not want to put my car on a dyno, rev it to high heaven (what is usually done on a dyno), and get detonation, or drive it down a 1/4 mi. track as fast as I can revving the engine up, and getting detonation. I was at the Racing Beat even and watched as Jim Mederer ran the test bench through the revs. The PCM was constantly monitoring the revs and changing the timing. At high revs the PCM was retarding the timing already. With 87 octane it would just be more so to protect the engine. This is not strictly a Mazda thing. All hi-performance engines pretty much have this feature. On my 911 it had this. In this case I'm not sure if anybody would offer up their car to test for this. Any takers ? About the closest test I ever saw done was in a Car & Driver once.
Last edited by Fanman; 10-08-2004 at 01:20 PM.
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I found the test :
http://www.caranddriver.com/article....&page_number=1
Enjoy. Notice the Honda didn't gain like I had thought, but the Saab & BMW M3 loss quite a bit of hp. And the Mustang 7 Dodge Ram gained a few hp (That gain in the 1/4 mi. by the Mustang is unbeliavable !!!
http://www.caranddriver.com/article....&page_number=1
Enjoy. Notice the Honda didn't gain like I had thought, but the Saab & BMW M3 loss quite a bit of hp. And the Mustang 7 Dodge Ram gained a few hp (That gain in the 1/4 mi. by the Mustang is unbeliavable !!!
#47
When you have an engine with 10:1 compression that freely spins to 9000+ rpm, why would you ever think of NOT putting the highest octane you can find in it To save 2 bucks per tank To get an extra 10 miles out of a tank? Read the decal inside of the fuel door...Premium Recommended. I run nothing but 93 every tankful. Consistant 19+ mpg runnin it hard with A/C on around town. No problems whatsoever with 10K miles. Nuff said...
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[QUOTE=bryrx804]Well I fill up with 93 every tank..cant find 91 no such number it goes 87, 89, 92 or 93 depends on the station.. Cheaper stations like speeway have 92.. which I dont go to.. only fill up a MOBIL or Marthon, and last SHELL.
Sunoco is one that you seem to find 91 at consistently. Most others jump from 89 to 93...
Sunoco is one that you seem to find 91 at consistently. Most others jump from 89 to 93...
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@Fanman:
that C&D article was a good link, thx. The article mixes absolute numbers (hp gains) with % numbers there (Accord lost 2.6% of hp) The 2.6% that the Accord lost, correspond to ~6hp.
3 questions about that.
1) Terms. Detonation = pinging = knocking? Is that all the same?
2) Frequent detonation harms (= damage) the engine, I can see that. But if the engine timing is adjusted, then it cannot harm the engine - only lose 5 or 10 hp. Did I get that right? I don't consider losing hp 'harming' the engine.
3) How do we know that the RX-8 is calibrated for high-octane gas? Because of the sticker? If it's calibrated for regular gas, there's a good chance that it cannot advance timing beyond their nominal ideal setting when burning premium.
Nope, I'm not providing mine for a test :-)
-Peter
that C&D article was a good link, thx. The article mixes absolute numbers (hp gains) with % numbers there (Accord lost 2.6% of hp) The 2.6% that the Accord lost, correspond to ~6hp.
Originally Posted by Fanman
[..]
but you are losing hp. Just because you are not hearing detonation doesn't mean it is not harming your engine.[..]
but you are losing hp. Just because you are not hearing detonation doesn't mean it is not harming your engine.[..]
3 questions about that.
1) Terms. Detonation = pinging = knocking? Is that all the same?
2) Frequent detonation harms (= damage) the engine, I can see that. But if the engine timing is adjusted, then it cannot harm the engine - only lose 5 or 10 hp. Did I get that right? I don't consider losing hp 'harming' the engine.
3) How do we know that the RX-8 is calibrated for high-octane gas? Because of the sticker? If it's calibrated for regular gas, there's a good chance that it cannot advance timing beyond their nominal ideal setting when burning premium.
Nope, I'm not providing mine for a test :-)
-Peter
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Originally Posted by ptiemann
@Fanman:
that C&D article was a good link, thx. The article mixes absolute numbers (hp gains) with % numbers there (Accord lost 2.6% of hp) The 2.6% that the Accord lost, correspond to ~6hp.
3 questions about that.
1) Terms. Detonation = pinging = knocking? Is that all the same?
2) Frequent detonation harms (= damage) the engine, I can see that. But if the engine timing is adjusted, then it cannot harm the engine - only lose 5 or 10 hp. Did I get that right? I don't consider losing hp 'harming' the engine.
3) How do we know that the RX-8 is calibrated for high-octane gas? Because of the sticker? If it's calibrated for regular gas, there's a good chance that it cannot advance timing beyond their nominal ideal setting when burning premium.
Nope, I'm not providing mine for a test :-)
-Peter
that C&D article was a good link, thx. The article mixes absolute numbers (hp gains) with % numbers there (Accord lost 2.6% of hp) The 2.6% that the Accord lost, correspond to ~6hp.
3 questions about that.
1) Terms. Detonation = pinging = knocking? Is that all the same?
2) Frequent detonation harms (= damage) the engine, I can see that. But if the engine timing is adjusted, then it cannot harm the engine - only lose 5 or 10 hp. Did I get that right? I don't consider losing hp 'harming' the engine.
3) How do we know that the RX-8 is calibrated for high-octane gas? Because of the sticker? If it's calibrated for regular gas, there's a good chance that it cannot advance timing beyond their nominal ideal setting when burning premium.
Nope, I'm not providing mine for a test :-)
-Peter
2. The engine timing can only go so far. Like you said with a batch of Costco 87 you ran into issues. 87 is the minimum standard of gasoline that you can put in the card. In essence you are at the far end of tolerance with where the PCM can retard your engine. Any lower, or a lower batch of 87 and you will possibly harm your engine. With 91, even if it is a slightly lower quality you will be OK.
3. According to the Owner's Manual the RX8 functions optimally with 91 octane fuel. From section 4-2 :
Your Mazda will perform best with fuel listed in the table :
Premium unleaded fuel - 91 or above octane rating
*You may use a regular unleaded fuel with an Octane Rating from 87 to 90 but this will slightly reduce performance.
* Fuel with a lower rating than 87 octance could cause the emission control system to lose effectiveness. It could also cause engine knocking and serious engine damage.
In this case our cars would function closer to the Saab & M3 as it is set to function with 91 Octane. It's PCM is set to function optimally with 91 (not just what is on the sticker, but the owner's manual as well). It's not a question of not being able to use 91 octane, as this is considered the nominal/regular/optimal setting of the PCM (If you use above 91 you will not see much improvement), not 87. The Mustang or Dodge Ram were set to function with 87 Octane as the normal standard for that vehicle (larger, lower compression engines)