andyfatsax
Member
- :
- Mazdaspeed3
Yes I am write and you are wrong...high octane = more power!
What octane do you put in your cars?
- Thread starter Khoifather
- Start date
andyfatsax
Member
- :
- Mazdaspeed3
Yes, i can explain...higher octane gives me more power, which means I can go faster than you. It's simple really.
No. You are wrong. Do you even know what octane is? Yes, there is a relationship between power and octane but not the way you think it is. A high compression engine usually means that engine puts out more power, that is why you need higher octane. So what that means is you need higher octane because you have a high power engine. It does not mean by putting higher octane will change mechanical properties of your engine (will not changes the compression ratio of your engine) to make it high power. It's like you need size 12 shoes if you have size 12 feet. If you have size 10 feet, by putting on size 12 shoes does not make your feet size 12 just because your feet will fit in them. You can still wear size 12 shoes but other than making your feel look bigger, they're really not.andyfatsax said:
What little gain you get from using higher octane fuel does not reflect the same level of gain an engine that is designed for higher octane gets.
I'm not telling you want to do and you certainly have the right to do what you want with your money. I'm not telling you to use lower octane fuel. But when you're providing misinformation without anything to back up your claim then that's wrong.
Now, going back to my first question, do you know what octane is? You don't have to buy my answer. Just ask a chemist, petroleum engineer, authorized factory mechanic, or anyone of credible credentials. I'm not saying I'm one of them. Just offering up another point of view.
Last edited:
rednecks_r_us
Member
- :
- 2003 Laser Blue Protege5
I run 91 octane. I have to. If I don't then I start pining.
Oh by the way I have an MP3 ECU in my MP5. (advanced timing)
Oh by the way I have an MP3 ECU in my MP5. (advanced timing)
i've used 91 when i first got my car thinking it would make my car go faster and burn cleaner. NOPE!!! its a misconception people think about which octane to put in there car. so every year i knocked my car down from 91 - 89 - *87* and 87 octance felt so much better. my car responds better, i get better mileage, and less carbon deposits left. Only high compressed engines require 89 and up. So stick with 87 for the Protege 5 and MP3! For turbo 91+ I just wish I knew that before I wasted my money on higher octane gas that doesn't benefit my car at all... 
johnjay5 said:i've used 91 when i first got my car thinking it would make my car go faster and burn cleaner. NOPE!!! its a misconception people think about which octane to put in there car. so every year i knocked my car down from 91 - 89 - *87* and 87 octance felt so much better. my car responds better, i get better mileage, and less carbon deposits left. Only high compressed engines require 89 and up. So stick with 87 for the Protege 5 and MP3! For turbo 91+ I just wish I knew that before I wasted my money on higher octane gas that doesn't benefit my car at all...
actually the mp3 does require higher octane. because of its advanced timing.
rednecks_r_us
Member
- :
- 2003 Laser Blue Protege5
The MP3 does have to run the high octane. And now so do I. Thats the trade off for smoother throttle responce, no more 1st gear bucking, better gas mileage and a little more HP.
I was thinking about which octane people were using in their P5's and I came across this old thread. I have read through every post and I thought I would share some of my observations.
First of all, I've only had my 2003 p5 for 3 weeks or so, it has 25k miles, and this is only the 2nd fillup. My first tank was 87, and it seemed to run fine. I then filled up with 91 and discovered the car is running a little smoother, particularly at 70+MPH. Throttle tip-in is also improved, and the car feels more responsive, but I didn't notice any change in power.
Now, from what I have learned about octane I believe there are some misconceptions on this thread.
One such misconception is that 91 vs 87 octane will somehow damage or foul your engine - I believe this to be patently false. It may not do you any good, but it will not harm your engine in any way.
Another is the nature of the burn relative to octane rating. As I understand it high octane does not burn hotter, or colder, and it is not resistant to ignition. It simply burns a little slower, which retards the flamefront somewhat, allowing the piston to reach TDC and start the power stroke before the flame forms fully. This can be very beneficial for engines that are prone to pre-ignition, especially turbo and high compression engines that can sometimes ignite the mixture during the compression stroke before the spark plug even fires.
Next topic is the formulation of different fuels. One thing you will find is higher octane fuels actually have better additives and generally keep your engine's internals (like injectors) cleaner. For example, Chevron adds techron to their premium fuel, which is one of the best fuel injector cleaners available. So in general premium fuels will help improve your engine's efficiency and longevity by preventing gumming and other buildups if nothing else.
Now, lets discuss engine management systems. This is an area that I have had to do much research into as I was building up my MR2 Turbo. But first lets discuss air/fuel ratios. The optimum (stoich) air to fuel ratio is typically 14.7:1 (14.7 parts air to 1 part fuel), regardless of octane. When the air/fuel ratio is higher (i.e. more air, less fuel) it is called lean, and when lower (more fuel, less air) it is called rich. Lean mixtures ignite faster and burn hotter, whereas rich mixtures ignite slower and burn cooler. Okay, now also consider that optimum ignition points variy from engine to engine based on a number of things, including the air/fuel ratio, air temperature (density), compression ratios, and a number of other things. Most engines fire the spark a few degrees before TDC on the compression stroke because the flame front usually takes a few milliseconds to form, and the more complete the burn the less emissions (better for the environment).
Most modern internal combustion engines today use some form of knock sensing device, and a computerized timing and fuel management system. To put it simply, the computer's job is to keep the engine running as efficiently and cleanly as possible throughout the rev range. Virtually all cars do this via an oxygen sensor and a knock sensor. The job of the oxygen (02) sensor is to sense how much oxygen is in the exhaust. The signal from the O2 sensor is picked up by the ECU (the engine's computer brain) and used to determine how long to fire the fuel injectors (thereby altering air/fuel ratio). When preignition occurs the resulting shock wave or vibration is sensed through a listening device called a knock sensor. The knock sensor is constantly monitored by the ECU. When knock is detected the ECU corrects by retarding the timing, or adding more fuel (altering the air/fuel ratio) or both. In my MR2 the ECU can take out as much as 10 degrees of timing to prevent preignition, and under high boost it can alter the air/fuel ratio from the optimum 14.7:1 to as much as 11:1 (rich).
So, how does this affect the fuel octane issue? Well, simple; if your ECU is sensing knock or preignition it is retarding timing and possibly adding more fuel (running rich). So, if preignition was previously present (even though you don't hear it - the knock sensor does) and you switch to a higher octane, the ECU will sense that knock has been reduced or eliminated and will advance the timing (or stop retarding) and/or lean the mixture, thereby improving power and fuel economy. Of course this assumes that your ECU is currently sensing knock with the fuel you are currently using, otherwise besides the better cleaning additives you will get absolutely no gain in power or mileage. The only way to be absolutely certain is to use a dynometer or some sophisticated diagnostic tools, neither of which are commonly available to most people. Another helpful tip is to pull the spark plugs and examine them. A rich engine will usually have some heavy black deposits. If the engine is experiencing a lot of knock the electrodes and/or the porcelain insulator may be pitted or chipped, but these symptoms are often very difficult to detect with an untrained eye.
There is just one more thing I'll add to this; as your engine ages various carbon deposits tend to form on the surfaces of the combustion chamber, the valves, pistons, etc. These carbon deposits often become hot spots, which can lead to preignition (knock). Another common cause is dirty or gummed up fuel injectors. When an injector gets fouled the spray pattern deteriorates and the fuel mix will lean out and cause the engine to knock and run hotter in the affected cylinder. These are two of the common reasons why some engines start pinging as they get more miles on them, thereby leading people to switch to higher octane to stop the pinging. Although a couple of tankfuls of premium may help clean the injectors and some of these deposits away, it usually doesn't do enough to permit the owner to go back to a lower octane without the pinging returning.
My recommendation is that you all use your own judgement. In my P5 I plan to run a tank of premium every other tankful or maybe every third tank to help with cleaning and to reduce carbon deposits. In your case YMMV. A bottle of techron or similar additive every 3 months may also help, but again YMMV. IMPO if you can prevent these problems from developing in the first place you'll be better off in the long run.
First of all, I've only had my 2003 p5 for 3 weeks or so, it has 25k miles, and this is only the 2nd fillup. My first tank was 87, and it seemed to run fine. I then filled up with 91 and discovered the car is running a little smoother, particularly at 70+MPH. Throttle tip-in is also improved, and the car feels more responsive, but I didn't notice any change in power.
Now, from what I have learned about octane I believe there are some misconceptions on this thread.
One such misconception is that 91 vs 87 octane will somehow damage or foul your engine - I believe this to be patently false. It may not do you any good, but it will not harm your engine in any way.
Another is the nature of the burn relative to octane rating. As I understand it high octane does not burn hotter, or colder, and it is not resistant to ignition. It simply burns a little slower, which retards the flamefront somewhat, allowing the piston to reach TDC and start the power stroke before the flame forms fully. This can be very beneficial for engines that are prone to pre-ignition, especially turbo and high compression engines that can sometimes ignite the mixture during the compression stroke before the spark plug even fires.
Next topic is the formulation of different fuels. One thing you will find is higher octane fuels actually have better additives and generally keep your engine's internals (like injectors) cleaner. For example, Chevron adds techron to their premium fuel, which is one of the best fuel injector cleaners available. So in general premium fuels will help improve your engine's efficiency and longevity by preventing gumming and other buildups if nothing else.
Now, lets discuss engine management systems. This is an area that I have had to do much research into as I was building up my MR2 Turbo. But first lets discuss air/fuel ratios. The optimum (stoich) air to fuel ratio is typically 14.7:1 (14.7 parts air to 1 part fuel), regardless of octane. When the air/fuel ratio is higher (i.e. more air, less fuel) it is called lean, and when lower (more fuel, less air) it is called rich. Lean mixtures ignite faster and burn hotter, whereas rich mixtures ignite slower and burn cooler. Okay, now also consider that optimum ignition points variy from engine to engine based on a number of things, including the air/fuel ratio, air temperature (density), compression ratios, and a number of other things. Most engines fire the spark a few degrees before TDC on the compression stroke because the flame front usually takes a few milliseconds to form, and the more complete the burn the less emissions (better for the environment).
Most modern internal combustion engines today use some form of knock sensing device, and a computerized timing and fuel management system. To put it simply, the computer's job is to keep the engine running as efficiently and cleanly as possible throughout the rev range. Virtually all cars do this via an oxygen sensor and a knock sensor. The job of the oxygen (02) sensor is to sense how much oxygen is in the exhaust. The signal from the O2 sensor is picked up by the ECU (the engine's computer brain) and used to determine how long to fire the fuel injectors (thereby altering air/fuel ratio). When preignition occurs the resulting shock wave or vibration is sensed through a listening device called a knock sensor. The knock sensor is constantly monitored by the ECU. When knock is detected the ECU corrects by retarding the timing, or adding more fuel (altering the air/fuel ratio) or both. In my MR2 the ECU can take out as much as 10 degrees of timing to prevent preignition, and under high boost it can alter the air/fuel ratio from the optimum 14.7:1 to as much as 11:1 (rich).
So, how does this affect the fuel octane issue? Well, simple; if your ECU is sensing knock or preignition it is retarding timing and possibly adding more fuel (running rich). So, if preignition was previously present (even though you don't hear it - the knock sensor does) and you switch to a higher octane, the ECU will sense that knock has been reduced or eliminated and will advance the timing (or stop retarding) and/or lean the mixture, thereby improving power and fuel economy. Of course this assumes that your ECU is currently sensing knock with the fuel you are currently using, otherwise besides the better cleaning additives you will get absolutely no gain in power or mileage. The only way to be absolutely certain is to use a dynometer or some sophisticated diagnostic tools, neither of which are commonly available to most people. Another helpful tip is to pull the spark plugs and examine them. A rich engine will usually have some heavy black deposits. If the engine is experiencing a lot of knock the electrodes and/or the porcelain insulator may be pitted or chipped, but these symptoms are often very difficult to detect with an untrained eye.
There is just one more thing I'll add to this; as your engine ages various carbon deposits tend to form on the surfaces of the combustion chamber, the valves, pistons, etc. These carbon deposits often become hot spots, which can lead to preignition (knock). Another common cause is dirty or gummed up fuel injectors. When an injector gets fouled the spray pattern deteriorates and the fuel mix will lean out and cause the engine to knock and run hotter in the affected cylinder. These are two of the common reasons why some engines start pinging as they get more miles on them, thereby leading people to switch to higher octane to stop the pinging. Although a couple of tankfuls of premium may help clean the injectors and some of these deposits away, it usually doesn't do enough to permit the owner to go back to a lower octane without the pinging returning.
My recommendation is that you all use your own judgement. In my P5 I plan to run a tank of premium every other tankful or maybe every third tank to help with cleaning and to reduce carbon deposits. In your case YMMV. A bottle of techron or similar additive every 3 months may also help, but again YMMV. IMPO if you can prevent these problems from developing in the first place you'll be better off in the long run.
Vanimaniac
Member
87 for the P5.
91 for the A4 (93 if we had it).
Van
91 for the A4 (93 if we had it).
Van
Nice post, thanks for the refresh. I always figured that since I got better gas mileage on Premium, that the engine was running more efficiently (more efficiency = more power, to some degree, right?).
FYI, Techron is present in all grades of Chevron gasoline, not just the premium grade.
FYI, Techron is present in all grades of Chevron gasoline, not just the premium grade.
solomr2 said:
andyfatsax
Member
- :
- Mazdaspeed3
See I told you, higher octane = more power. Everyone should use 91 octane.
PMPJUICE25
Member
- :
- MAZDA PROTEGE 5
89 Octane Does Great For Me. It Burns Faster If Ou Step On It Though. But The Car Seems To Run Smoother With It To Me.
