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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHBellevue, WA area high octane gas?
Leading reported evidence
Adjust on the first tank
Suggestion or failed attempt
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Discussions that contain suggestions
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Leading evidence: 'Adjust on the first tank' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'lower octane gas' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Adjust on the first tank' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that suspect a cause
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Suspected cause
If the ECU detects that the gas is igniting by compression before the spark, which is caused by lower octane gas, it immediately adjusts and compensates by detuning the engine (changing the timing).
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion
If the ECU detects that the gas is igniting by compression before the spark, which is caused by lower octane gas, it immediately adjusts and compensates by detuning the engine (changing the timing).
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion
With 93 octane or better (and no carbon problems) the spark timing is advanced as far as it goes, so there is no point to running above 93 on the street with the stock ECU.
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Suggestion
If you are using 93-94 octane, the gas will be able to withstand the compression and will properly ignite with the spark.
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Suggestion
If the ECU detects that the gas is igniting by compression before the spark, which is caused by lower octane gas, it immediately adjusts and compensates by detuning the engine (changing the timing).
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
With 93 octane or better (and no carbon problems) the spark timing is advanced as far as it goes, so there is no point to running above 93 on the street with the stock ECU.
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Suggestion
Conversely, using low octane fuels in these cars will simply make the engine not feel very crisp and you will not have full power until you use better fuel.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
lower octane gas
No successful repair reported for this finding.
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Identified cause
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Suspected cause
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Reported fixes
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Discussions that suspect a cause
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause
If the ECU detects that the gas is igniting by compression before the spark, which is caused by lower octane gas, it immediately adjusts and compensates by detuning the engine (changing the timing).
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
14 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261027T011819Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Just read the topic on octane and have been running Chevron 92 octane in my 996 since I purchased it. Thought I'd give a try to something a little higher if I could find it. Does anyone here happen to live near Bellevue WA and know of stations that sell 94 or above?
Thanks!
I don't know the geography of WA, but the following two 76 stations in the state sell 100 octane gas:
8325 MUKILTEO SPEEDWAY (Intersection of CASINO and MUKILTEO SPEEDWAY)
MUKILTEO, WA
Phone [phone removed]
212 E COLLEGE WAY (Intersection of I-5 and COLLEGE WAY)
MT. VERNON, WA
Phone [phone removed]
Good luck!
Craig (L.A.)
You might get better performance with octane ratings above 92 but I doubt if it will be the result of the computer retuning or reseting.
It is likely no one designing the engine ecu firmware had the forethought, or any reason for, accomodating anything higher than 92. Their focus would have been on preventing engine problems with lower octane fuelings.
Rob,
I am not a techy guy, but I'll try to answer your question. Everytime you start the engine, the ECU immediately and constantly monitors how the gas is igniting in relationship to the spark (which is directly related to the octane level of the gas). If the ECU detects that the gas is igniting by compression before the spark, which is caused by lower octane gas, it immediately adjusts and compensates by detuning the engine (changing the timing). If you are using 93-94 octane, the gas will be able to withstand the compression and will properly ignite with the spark. The ECU will detect this proper ignition and will not make any adjustments. Stated another way, the ECU only intervenes if the octane is insufficient. Given that your ECU is contantly monitoring these issues (many times per second), it will immediately react to higher octane gas as soon as you start your car after filling your tank (actually, the ECU will react by NOT reacting if you put in higher octane gas). Therefore, the performance benefits will be immediate.
Hope that helped.
Craig (L.A.)
Another way to look at is that the ECU is aggressive, and will advance the spark until pre-ignition is detected by the piezo (probably) sensor. As Craig writes, it is checking this many times every second.
With 93 octane or better (and no carbon problems) the spark timing is advanced as far as it goes, so there is no point to running above 93 on the street with the stock ECU.
On the track or with a turbo more octane may add a valuable margin of safety given the much higher heat stress.
So it sounds like a half tank 92 and half 100. Thanks for the insight. Jim - Issaquah, I grew up on Tiger Mtn. Small world.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
2-3 gallons should be enough on 92, there may not be any advantage at all to more. You are also not losing as much as those of us on 91 octane, so the effect will be less noticeable.
[quote]Originally posted by wwest:
<strong>Many small airports "service" will fill you up with 100 octane. Or put 10 gallons of 92 in and then filler-up.</strong><hr></blockquote>
Hi:
If I may step in here a moment,..
Never, ever put in any aviation fuel. ALL of it has lead and will ruin your cats on the very first tank. Further, your oxy-sensors will get coated with lead and the manganese salts uses in aircraft gasolines and you'll buy those, too.
Use unleaded race gas if you need better fuel.
FWIW, the ECU is programmed (Factory or ours) to advance & retard igntion timing within a pre-programmed range at all RPM and throttle openings. When you use 93-94 octane fuels, over 91-92 octane fuels, you will get an immediate performance increase (more torque) due to the ECU permitting the full amount of timing programmed into the software. Conversely, using low octane fuels in these cars will simply make the engine not feel very crisp and you will not have full power until you use better fuel.
ECU re-programming will permit even more power provided that you use the proper fuel for the software changes that were done. Its quite noticeable.
[quote]Originally posted by Steve Weiner-Rennsport Systems:
<strong>
Use unleaded race gas if you need better fuel.
</strong><hr></blockquote>
OK, where in the Portland/Vancover area is the place to find that? <img src="confused.gif" border="0">
[quote]Originally posted by CarreraFour:
<strong>
OK, where in the Portland/Vancover area is the place to find that?
</strong><hr></blockquote>
Its tough to find as there are no gas stations selling unleaded race gas. I buy it by the 55 gallon drum during the race season, as I need it.
Competition Specialties & Matrix Engineering usually have it around, just bring some gas cans.
This is a source reference. Confirm exact model applicability in the original material.
