So gas prices are going up again, and I'm wondering if it's *really* necessary to use the high-grade 93 octane. Has anyone used mid-grade (89 octane) in their MSPs? For what it's worth, my Speed is stock, non-flashed, and I usually don't push above 4500-5000 RPM (not enough open road in everyday commuting).
89 octane anyone?
- Thread starter velokid
- Start date
evo..eater:)
Member
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- 2003.5 Mazdaspeed Protege
I would not recommend it. I have always run 93 octane in my vehicle. It is a little bit more expensive but I feel that it is well worth it. No risk to enginge failure.
jersey_emt
Member
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- 04 MSM #1089
Yes...do NOT run less than 91 octane.
Chances are if you run 89 nothing bad will happen...but if something does, say good bye to your warranty. Mazda will definitely void it (and rightfully so).
Chances are if you run 89 nothing bad will happen...but if something does, say good bye to your warranty. Mazda will definitely void it (and rightfully so).
The difference in price b/w 89 and 91 is usually only about $0.05/gallon +/-. In a worst case scenario, let's say $0.10. Now assuming you fill up only when the dummy light comes on (as I do) then you will be pumping in ~ 12+ gallons. So that's an extra $0.60 - $1.20 per fill up. Extrapolate that over the course of a year (assuming one fill-up per week) and you are talking anywhere from an extra $30 - $60 per year for the higher octane gas.velokid said:
The cost (risk associated with using lower octane gas) far outweighs have a couple quarters in your pocket. If you are really keen on saving some change, go to an area that's densely populated with gas stations. Since they compete with each other price-wise, one will always be a couple cents lower than another (per gallon).
Ben
Got_boost02
Member
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- Titanium MSP
its always better to run as high an octane as you can
DistantTea
Member
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- Mazdaspeed... of DOOM!
You people sound like the bush administration... voided warranties? detonation? WTF? The difference in 87 octane and 93 octane fuels is entirely a performance issue. If you run 87 on a super hot day and you just happen to be drag racing yes, there is a chance that at some point you could ping. But with stock boost and those rich fuel maps... not bloody likely. What'll happen is your timing will get pulled and the car will run like.. well like you put bad gas in it. So if you live in south florida, run high boost, and drag race... no don't use lower octane fuels.
But like the others said you're only saving $2 a tank... why bother putting horse killing piss water in there? It'll just slow the car down. $2 a week to keep the smile machine running at full steam is worth it to me.
But those gloom and doom answers are a bit far fetched in my opinion.
But like the others said you're only saving $2 a tank... why bother putting horse killing piss water in there? It'll just slow the car down. $2 a week to keep the smile machine running at full steam is worth it to me.
But those gloom and doom answers are a bit far fetched in my opinion.
jersey_emt
Member
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- 04 MSM #1089
Yes you are right, the PCM *should* pull timing if you put bad gas in it. But who really wants to try to see if it does so correctly?DistantTea said:
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- 2003.5 Mazdaspeed Protege
what would running 100 octane do to the car???????? any problems?????? i saw they had it at this station today. 4.99 a gallon.....i figured what the fu*k....i put a gallon in....doubt it did anything.....what would be a good mixture to run if not straight?
Got_boost02
Member
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- Titanium MSP
the higher octane you run, the more safeguard you have against detonation at higher boost levels
DistantTea
Member
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- Mazdaspeed... of DOOM!
But without a learning ecu higher octane dosn't add horsepower. Since we use those blasted maps all higher octane fuel does for you is make sure you get to use everything thats mapped. On a german car, like an Audi, you can actually make some pretty huge gains through higher octane fuel.
DSMConvert
AWD...say Bye Bye
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- Titanium MS6
ok first off 89 octane will NOT void your warranty...well technically it can, but it would require well over 1200 in tests to prove that the octane rating of the fuel in the tank is 89...if you've ever noticed gas stations use the R/2 method...but for proving it in a court of law or contractual agreement you must be within an error level of alpha=.05....95% confidence level for you statistics freaks out there....Id dare to say 98% or dealerships wouldnt even consider gas an issue... now secondly, being as that our cars run notoriously rich we can get away with running a lower octane fuel...I highly doubt you'll ping at stock boost with a 14.4 a/f (dyno proven). As far as running higher octanes, the only reason you would want to do this is to make the a/f mixture more combustable...as more air is forced in(higher boost) you must be able to keep the same ratio...for example 90octane and 100cfm means a particle mixture of 9parts octane to 10 parts air...to keep this same combo for 200cfm you'd have to double your octane...this is a very very simple example and not even close to the actual case of our cars but gets the point across. You must be careful though b/c as you get higher in octane you get closer to leaded fuel which is very very very very bad for engines and o2 sensors...ok nuff said...
-John
-John
Higher octane doesn't make the A/F mix more combustible. The only reason to run higher octane is to achieve a more controlled burn of the A/F mix - which is why it is a safeguard against knock.
Long story short, you'd be safe running 89 octane if you wanted to. The fuel mix is plenty rich to avoid pinging plus the PCM will pull timing anyway if it senses knock. Running higher octane than necessary can give you LESS power if the A/F mix isn't burning completely...so if you're not upping the boost or advancing the timing there's no point at all in running higher octane. In fact, running too high of octane too often has the potential to lead to carbon deposits in the engine -- which in turn can end up being "hot spots" -- which in turn can result in the very thing you were trying to avoid - an uncontrolled burn.
It's technically possible that you'd not only save money but actually feel a power increase if you switched to 89 octane. That should not happen in a properly tuned turbo vehicle but we all know the MSP is a long shot from properly tuned.
Long story short, you'd be safe running 89 octane if you wanted to. The fuel mix is plenty rich to avoid pinging plus the PCM will pull timing anyway if it senses knock. Running higher octane than necessary can give you LESS power if the A/F mix isn't burning completely...so if you're not upping the boost or advancing the timing there's no point at all in running higher octane. In fact, running too high of octane too often has the potential to lead to carbon deposits in the engine -- which in turn can end up being "hot spots" -- which in turn can result in the very thing you were trying to avoid - an uncontrolled burn.
It's technically possible that you'd not only save money but actually feel a power increase if you switched to 89 octane. That should not happen in a properly tuned turbo vehicle but we all know the MSP is a long shot from properly tuned.
