Octane
- Thread starter fkmp5
- Start date
- :
- 10 MS3
Hmmmmmmmm I use 89.
the engines are built and made for 87. Unless you have ported or made serious mods to the engine (eg. turbo, pistons, etc..) there is no need to up the octane. Things like CAI, exhaust, plugs, etc... do not need nor benefit from a higher octane. This is a popular misconception. Octane ratings are a measurement of the fuel's ability to resist engine knocking or pinging. The knock results from uneven burning of the compressed fuel-air mixture. Our engines are built to not knock on 87. Also, remember this is a manufacturer's conservative number. We actually could DROP octane (eg 86 or whatever) and probably run fine, but Mazda has determined 87 is sufficient without knocking. Upping to a higher octane will not gain you power nor will it give you better gas mileage. Our engines "auto-adjust" to new octanes, so we will always get the correct air-to-fuel ratio needed to run the engine smoothly. I used to put 91 in my Avenger, but when $$ was low, I just threw in 87. There was NO difference in performance or fuel economy.
Don't confuse higher octane with fuel additives that are included in a certain makers fuel. Example, a high octane fuel doesn't keep your engine parts cleaner than a lower octane. Those are additives that the fule maker adds to help attract consumers and make their fuels more desireable. Example, Chevron gasoline with Techron. Techron is the additive in the fuel that will help keep the engine parts the fule comes in contact with free from substantial residue. A higher octane does not atomatically give you this. higher Octane doesn't equal cleaner fuel.
I found some stuff on the net, so if you want more detailed info on this read below. Fuel octane has always been a questionable subject. Some people feel strongly that a higher octane is worth it. Personally, unless I am running turbo + nitrous +etc.., I wouldn't up the octane. Under those intense conditions, Engine knocking may be more prone to happen, and the increase would be necessary, but without SUPER mods, I think you're throwing your $$ away.
Read below for more info:
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.
Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.
Can I mix different octane fuel grades?
Yes, however attempts to blend in your fuel tank should be carefully
planned. You should not allow the tank to become empty, and then add 50% of
lower octane, followed by 50% of higher octane. The fuels may not completely
mix immediately, especially if there is a density difference. You may get a
slug of low octane that causes severe knock. You should refill when your
tank is half full. In general the octane response will be linear for most
hydrocarbon and oxygenated fuels eg 50:50 of 87 and 91 will give 89.
Attempts to mix leaded high octane to unleaded high octane to obtain higher
octane are useless for most commercial gasolines. The lead response of the
unleaded fuel does not overcome the dilution effect, thus 50:50 of 96 leaded
and 91 unleaded will give 94. Some blends of oxygenated fuels with ordinary
gasoline can result in undesirable increases in volatility due to volatile
azeotropes, and some oxygenates can have negative lead responses. The octane
requirement of some engines is determined by the need to avoid run-on, not
to avoid knock.
Can I tune the engine to use another octane fuel?
In general, modern engine management systems will compensate for fuel octane,
and once you have satisfied the optimum octane requirement, you are at the
optimum overall performance area of the engine map. Tuning changes to obtain
more power will probably adversely affect both fuel economy and emissions.
Unless you have access to good diagnostic equipment that can ensure
regulatory limits are complied with, it is likely that adjustments may be
regarded as illegal tampering by your local regulation enforcers. If you are
skilled, you will be able to legally wring slightly more performance from
your engine by using a dynamometer in conjunction with engine and exhaust gas
analyzers and a well-designed, retrofitted, performance engine management
chip.
Don't confuse higher octane with fuel additives that are included in a certain makers fuel. Example, a high octane fuel doesn't keep your engine parts cleaner than a lower octane. Those are additives that the fule maker adds to help attract consumers and make their fuels more desireable. Example, Chevron gasoline with Techron. Techron is the additive in the fuel that will help keep the engine parts the fule comes in contact with free from substantial residue. A higher octane does not atomatically give you this. higher Octane doesn't equal cleaner fuel.
I found some stuff on the net, so if you want more detailed info on this read below. Fuel octane has always been a questionable subject. Some people feel strongly that a higher octane is worth it. Personally, unless I am running turbo + nitrous +etc.., I wouldn't up the octane. Under those intense conditions, Engine knocking may be more prone to happen, and the increase would be necessary, but without SUPER mods, I think you're throwing your $$ away.
Read below for more info:
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.
Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.
Can I mix different octane fuel grades?
Yes, however attempts to blend in your fuel tank should be carefully
planned. You should not allow the tank to become empty, and then add 50% of
lower octane, followed by 50% of higher octane. The fuels may not completely
mix immediately, especially if there is a density difference. You may get a
slug of low octane that causes severe knock. You should refill when your
tank is half full. In general the octane response will be linear for most
hydrocarbon and oxygenated fuels eg 50:50 of 87 and 91 will give 89.
Attempts to mix leaded high octane to unleaded high octane to obtain higher
octane are useless for most commercial gasolines. The lead response of the
unleaded fuel does not overcome the dilution effect, thus 50:50 of 96 leaded
and 91 unleaded will give 94. Some blends of oxygenated fuels with ordinary
gasoline can result in undesirable increases in volatility due to volatile
azeotropes, and some oxygenates can have negative lead responses. The octane
requirement of some engines is determined by the need to avoid run-on, not
to avoid knock.
Can I tune the engine to use another octane fuel?
In general, modern engine management systems will compensate for fuel octane,
and once you have satisfied the optimum octane requirement, you are at the
optimum overall performance area of the engine map. Tuning changes to obtain
more power will probably adversely affect both fuel economy and emissions.
Unless you have access to good diagnostic equipment that can ensure
regulatory limits are complied with, it is likely that adjustments may be
regarded as illegal tampering by your local regulation enforcers. If you are
skilled, you will be able to legally wring slightly more performance from
your engine by using a dynamometer in conjunction with engine and exhaust gas
analyzers and a well-designed, retrofitted, performance engine management
chip.
- :
- 2001 Mazda MP3
95? u live in a different country, is it the same measurement?
hey do you know in Hong Kong they only have 98? Talk about high-octate gas.... and as you might have guested they cost a fortune, 2 liter of those things can buy me a McDonald value meal there.... My dad drives a Lexus LS-400 in Hong Kong, and it costs him around $600 HKD which is around $76 USD per tank which is good for a week for him..... scary.....
banned bandit
Member
87 when cash is low, and 89 usualy
7
70
pdhaudio said:
They use a different rating system than the US...
7
70
mopiko said:
7
70
JAC said:
I thought the US was only country that used the averaging of both octane measurings to get the octane rating we have.
PS - I answered the poll as to what gas I would use if I had a stock Protege 5, which was 87.
I run 91 in my MP3 though.
- :
- '08 Jetta; '10 Wrangler Unlimited
Mine runs fine on 87. Will run a tank of 89 through every couple of months and don't notice any difference. Low compression engines don't require high octane fuel.
-R
-R
black&chromep5
Member
i run 87 in my p5. i ran 115 in mine once before and it ran like s***. let a guy that sells vp raceing fuel talk me into it. in the 8th i actually lost about 2 tenths. i dont know if it has any thing to do with it but right now my p5 is in the shop getting a new engine put in. pretty much i think i just turned stupid. it would make a difference in a built car but not in a stock p5. it will just hurt you. live and learn.
car runs fine with 87. it's not "hi performance," so there's no need to run anything higher. if you up the compression ratio or if you go turbo, then something higher would be required to avoid knocking. otherwise, you are just giving the gas companies more of your money. each fill up is about an extra $2.50 if you go 91 or 93 octane compared to 87. if you fill up weekly, that's about $130 a year you would have given to the gas companies for no gains. your car won't run cleaner, it won't give you more gas mileage, nothing. just go with 87 and use that $130 towards mods.
