91 Octane issues?

[tokiokun717]

Just read this article and was wondering if anyone is experiencing similar inconsistent power issues issues because of the crappy fuel.

http://www.motoiq.com/magazine_artic...strations.aspx

if this is true, it's going to change the way I spend my money...

[jlu]

Just from driving feel (no numbers here), the car does feel sluggish after spirited driving through hills in cold weather. Not sure if that's related to CA gas or if the car just hates cold weather in general.

I haven't noticed any power loss or the car being sluggish, it runs the same all the time except for when its warming up, but at the same time i take it easy while its getting to optimum temp. I always let it run for about 5 min from cold start. This is also with only driving feel.

[jwcdis]

in California, during the winter time, gas manufacturers are allowed to produce a "winter blend" which is lesser/cheaper than other seasons that might have something to do with it.

Jerry Brown approved to have the winter-blend gas out earlier than usual this season.

I'm not big on the details like how it could affect performance but here is some extra reading material
http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm

[Clipdat]

I notice way more of a throttle hesitation/sluggishness with 91 Chevron, than when I filled up in San Leandro w/ 93.5 octane.

Definitely recommend the 93.5 if you can afford it @ $5.78/gal. Throttle response is snappy and awesome, need to fill up with it again...

[tokiokun717]

I guess the main issue I have here is that they are claiming that the ECU does some weird adjustments which negates a lot of the hp benefits of the intake, exhaust, and even ECU tuning. If that's the case, I really don't see the point of investing money for parts to increase power...

Or I have to fill up at San Leandro all the time.

[mkiisupra]

From the 'off-topic' NorCA thread, thought it would be better here. Just yesterday I spoke about blending gas to get to the 93 octane, when you can find 100+ octane pumps.

Originally Posted by BlaineWasHere

There is no way mixing a little 100 octane gives more power. It's been proven.

I find no evidence that this WOULDN'T work, please share your data.

I respectfully disagree. Mixing high/low octanes w.r.t. volumes will result in an average octane based upon volume ratios. There are too many octane calculators and direct statements from petroleum distributors to deny that there is not octane boost from mixing lower octane with higher octane. However, the old myth that you will get a higher octane rating from the mix than either two in the mix is, indeed, false.

Several octane calculators show that the ~2.5 gal of 100 octane with CA's 91 in the rest of the tank calculates to about 93 octane. (

Eric G

[strat61caster]

You do know that no gas station has a "mid range octane" (89 here) tank right? It's just the high and the low mixed.

Here's the important bit, octane does not equal power. Octane rating indicates the fuel's resistance to pre-ignition or knock which is advantageous for various thermodynamic reasons. Our cars have a 12.5:1 compression ratio, this is pretty high, but it was designed for 91/93 octane fuel. If you run the proper fuel you get everything delivered to the wheels as advertised, a lower octane means that the charge (intake gasses and fuel) will preignite and knock, the engine will compensate by retarding the timing which results in reduced power.

RUNNING A HIGHER OCTANE WILL NOT MAGICALLY CHANGE HOW THE ENGINE WAS DESIGNED AND ADVANCE THE TIMING TO GIVE YOU MORE POWER. You may notice a difference, hell there may be clear statistical gains to it, but for 99.99% of consumers it won't do anything except drain your bank account a little faster. (Feel free to point me to resources showing the subieyota making statistically significant gains or losses for certain fuels, I would love to see it. Especially if there's a 93 vs. 91 octane comparison, $5 says there's no difference.)

As for winter blends and this vendor vs. that vendor, the octane rating is the same everywhere, from a purely basic thermodynamic standpoint it's all the same the engine will run pretty much the same and you're probably wasting time worrying about it. Some vendors will have different detergents and processes for refining (not many, there are only so many refineries shipping stuff out, there isn't as much variation as you think there is, it's all ridiculously regulated) which may result in a slightly different "soup" from one brand/station to the next, statistically speaking it's pretty much insignificant. The winter blend is a little cheaper, a little more polluting than what we use in the summer (thanks smog!) because it doesn't get jammed up in the atmosphere, it's a bit less efficient.

The only time you should worry about what you put in the tank is when you start running tunes and mawds and screwing with what the car was designed to run as, in that case you're pretty much relying on your tuner/vendor and whatever research he's done.

/rant required in every thread about gasoline ever.

[mkiisupra]

I don't disagree one bit with above. I am not looking for more power as asssumed in the above quote. My only goals are to try to feed the car with 93 as it was intended. The 91 allowance is just that, an allowance for those who cannot get 93. I don't mind spending a few $$ to feed my car the best I can. Because the 12.5/1 ratio is incredibly high, I do want to get as much octane to prevent said predetonation. I haven't, nor will I attempt anything like this in any of my other rides, but I believe ( and I wouldn't have a problem admitting being incorrect here) that this car is sensitive to gas, probably due to the 12.5/1 ratio more than anything else.

My only assertion is that 93 octane gas is acheivable by blending 100 and 91, that is the only claim I am making; heck, other's have disagreed with even that statement.

From what I read in the post above, it is suggested that there is no difference b/w 91 and 93 for these cars. While dyno and other data would be best for this comparo, we just have anecdotal experiences and stories to work with, so opinions rule the day.

I just do it for to reassure myself I am trying to best by my car. And it would seem, to drain my bank account faster...

Eric G

[BlaineWasHere]

Originally Posted by mkiisupra

From the 'off-topic' NorCA thread, thought it would be better here. Just yesterday I spoke about blending gas to get to the 93 octane, when you can find 100+ octane pumps.




I find no evidence that this WOULDN'T work, please share your data.

I respectfully disagree. Mixing high/low octanes w.r.t. volumes will result in an average octane based upon volume ratios. There are too many octane calculators and direct statements from petroleum distributors to deny that there is not octane boost from mixing lower octane with higher octane. However, the old myth that you will get a higher octane rating from the mix than either two in the mix is, indeed, false.

Several octane calculators show that the ~2.5 gal of 100 octane with CA's 91 in the rest of the tank calculates to about 93 octane. (

Eric G

I'm not saying that mixing in higher octane fuels doesn't give a higher octane but the ECU won't translate that into more power becuase it isn't taking advantage of the fuel with advanced timing.

If you have a 100 octane tune on your car 100 octane would certainly provide a substantial power boost. This is the theory behind e85 tuning because it's 104 octane and cheap!

So yes you can "make" 93 octane if that's what you're trying to do, it just isn't going to make you faster.

[strat61caster]

Originally Posted by mkiisupra

From what I read in the post above, it is suggested that there is no difference b/w 91 and 93 for these cars. While dyno and other data would be best for this comparo, we just have anecdotal experiences and stories to work with, so opinions rule the day.

The thing is, it isn't just anecdotal evidence, the manual says specifically that 91 octane is usable without any adverse effects (p. 56 of Scion manual). Until I see otherwise 91 = 93 in terms of performance for this vehicle, as per the manual. If I see 93 you bet your ass I'm going to use it, but I'm not going to waste time and money seeking it out. I'm not going to try and convince you otherwise, if it makes you feel confident in the longevity/performance of your vehicle then go for it. Different strokes for different folks. I am perfectly willing to accept defeat with evidence.

btw a general statement; don't bother with aircraft fuel, that stuff's got lead in it and will probably poison your catalytic converter over time.

[BlaineWasHere]

My car runs just fine on 91. My chrips are even gone. I'm also over 20K miles already. I only fill up at Shell or Chevron 91.

[PMok]

Originally Posted by strat61caster

The thing is, it isn't just anecdotal evidence, the manual says specifically that 91 octane is usable without any adverse effects (p. 56 of Scion manual). Until I see otherwise 91 = 93 in terms of performance for this vehicle, as per the manual. If I see 93 you bet your ass I'm going to use it, but I'm not going to waste time and money seeking it out. I'm not going to try and convince you otherwise, if it makes you feel confident in the longevity/performance of your vehicle then go for it. Different strokes for different folks. I am perfectly willing to accept defeat with evidence.

btw a general statement; don't bother with aircraft fuel, that stuff's got lead in it and will probably poison your catalytic converter over time.

I posted this in the off topic thread but will repost here too as its on point.
I'll quote from the BRZ manual...

The engine is designed to operate at maximum performance using
unleaded gasoline with an octane rating of 93 AKI (98 RON) or
higher. If 93 AKI (98 RON) fuel is not readily available in your area,
unleaded gasoline with an octane rating of 91 AKI (95 RON) may be
used with no detriment to engine durability or driveability. However,
you may notice a slight decrease in maximum engine performance
and you may hear some knocking (pinking) of an engine while using
91 AKI (95 RON) fuel. Use of 91 AKI (95 RON) fuel will not affect your
warranty coverage.

p. 420, BRZ owner's manual.

[mkiisupra]

Thanks PMok, that is the line that I was referring to when in pursuit of the not readily available 93 in my area.

Eric G