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2009 CTSV, silver, manual
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Discussion Starter #1
I am confused about Sunoco Ultra94 fuel, 94 octane is good but it is done with a 10% ethanol blend. The V wants 93 octane and I am not sure there is any benefit to any octane level above 93. If the 94 octane level provides no additional benefit against detonation (max timing already at 93 octane) then the 10% ethanol by volume would actually decrease the energy content per unit of fuel, ethanol has less BTU energy than pure gasoline. So, is it better to use 100% gasoline 93 octane, or the 94 octane Sunoco premium with 10% ethanol (93 octane gasoline blended up to 94 octane)? Anybody have a preference? I have researched this and it seems to be a point of argument. I don't know if our SC engines benefit more from the higher octane or less from the 10% ethanol content.
 

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2012 CTS-V Sedan, 2011 CTS Coupe, 2010 Ford Raptor
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Don't know if it's true or not but I've heard if it's hot (probably 85+), or you're running the car hard; an octane rating above 93 would help to ensure you don't have any knock.

Some may call BS on this... but when I had an '04 V I had half a tank of 93 then added 100 for the remaining half, and the car ran better (smoother). The other noticable difference was the smell of the 100 octane fuel, can't really describe it but I'd know it if I smelled it again.
 

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11v,2 09 v's,2 05 v's,5 GTM supercars,viper,volt,2012 karma
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I use the 94 in all my cars. 3 gas stations have it here. Where does it say that v power dont contain the manditory 10% ethonol?
 

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Cadillac 2009 CTS-V Radiant Silver
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I use the 94 in all my cars. 3 gas stations have it here. Where does it say that v power dont contain the manditory 10% ethonol?
*****************************

Out here in leftist land in Oregon, the Feds require 10% corn mash

Did not know Shell was exempt.....
 

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2008 CTS
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Probably regionally based.

I know that the shell station by me, the pumps state that 87/89 octane both contain ethanol, but 91 (v-power) contains no ethanol.

best bet is to call them..

General inquiries related to Shell Service Stations

(questions, comments, service station locator)
Phone: 888-GO-SHELL (888-467-4355)
E-mail: [email protected]
 

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'09 CTS-V Auto, Thunder Gray, Lt. Titanium, Recaro's, Loaded
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67 Posts
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Down here in Texas, IIRC the pumps are required to have a sticker on them stating they have 10% ethanol if the fuel is formulated as such. In theory, no sticker, no ethanol... Which helps finding non-ethanol fuel if you trust the stations to use the stickers, or to put non-ethanol fuel in the tanks.

But that brings on another matter most don't think about, at least down here. Just because a station says "Shell" or "Exxon" on it doesn't necessarily mean you are getting that brand of fuel. Gasoline down here often comes from bulk suppliers who have contracts to deliver gasoline to any number of branded stations. There is a local bulk fuel supplier down here who supplies all sorts of stations, and I have seen their trucks off-loading fuel at Valero, Exxon, and other branded stations. Hence, you often don't REALLY know what you're getting... :hmm:

Another problem down here with premium, higher octane fuel is the slow sale of it relative to lower octane fuels. Often at slower volume stations the premium sits in the ground a long, long time, which can lead to it having a lot of water and contaminants in it. Lower octane fuels sell better and turn over more so they are less likely to have trash and gunk in them, Your only defense in driving a car that requires high octane gasoline is to fill up at newer stations, with newer tanks, and that do a high volume business... And to stick to stations that use the stickers and look like they follow the drill of putting non-ethanol fuels in those tanks for those pumps without the stickers.

I ran into the problem this past weekend while I was up in Denton. I had to go to three stations to find one that had pumps not showing "10% ethanol" stickers, and oddly enough the station that had non-ethanol fuel was a bright, shiny, new Shell station.

Who really knows what is in those in-ground tanks or what is really coming out of them? All I guess you can do is try and trust the pump and hope for the best... ;)

Dallara




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2009 CTS-V (MG9)
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In Canada, we have Chevron gas stations that carry Chevron Supreme Plus 94. It is 94 octane without ethanol. I only use this fuel in all my cars.
In the past, I've tried all other fuels and would end up with pinging when hot under load in any of my performance vehicles. This does not happen when I use the Chevron 94 octane.
 

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2010 CTS-V
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Around Commietown, I mean Chicago, all grades contain 10% ethanol.
 

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2009 CTSv & 2006 STSv + 1991 SHO
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It would be good to know if Sunoco 94 makes any difference... I just filled up the 09V again last night with it and have been using it in the STSv as well for years. Not sure if it helps but I didn't think it could hurt.

A have a few friends with 1.8T VW GTIs which are chipped and require 94. I wonder if there is a tune that would take advantage of different octane levels.
 

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2009 CTSV, silver, manual
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Discussion Starter #16
The rquirement for 10% ethanol seems to be a regional thing. Around here (Indiana) I have seen pumps advertise 100% gasoline, and others seemingly randomly say 10% ethanol, and others still say nothing. I have seen 93 octane at Shell V-power and Amoco Ultimate. Sunoco has the Ultra94 which is an ethanol blended 93 octane gas to reach 94 octane.

As to the question of bulk fuel suppliers delivering fuel to multiple branded stations, this could be true. Gasoline is fungible, and the difference in the branded preimums (V-power, Amoco Ultimate, Ultra94, etc) are the additives added at the bulk terminal prior to trucking to retail stations. A tanker full of generic 87 octane will fill any brand, but a load of Ultra94 should have a unique blend at the bulk terminal.

All else equal I would believe a 100% gasoline premium 93 octane would be preferable to a 94 octane 10% ethanol blend. The difference might be unmeasurable or non-existant, I have no data for proof to know though. I assume that IF there is no detonation and the timing is optimal on 93 octane then running anything greater than 93 octane is just wasting money. Add to it the possible negative aspects of a 10% ethanol blend in 94 octane, it becomes even more likely that pure 93 octane is preferable, if you can find it.

I wonder how long it takes the ECM to advance timing after adjusting for detected knock? Does it know when fuel is added ot the tank and perhaps advance timing in stepwise fashion after a refuel? Or on engine restart does it reset? I also assume the knock sensors are more sensitive than my ear, and might detect knock and retard timing without me knowing it (on 91 octane perhaps)?

I would love to see a dyno done with 91 octane, 93 octane no ethanol, and 94 octane with 10% ethanol. I wonder if the difference would be noticeable, I bet it would if you could isolate all other variables.
 

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2009 CTSV, silver, manual
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Discussion Starter #17
OK this is bugging me, let me put some rough numbers to it to try to prove a point. Let's take a 10% ethanol 94 octane Ultra94 as an example. Ethanol has approx 70% of BTU per unit volume as gasoline, and at a 10% blend by volume that yields about 97% of BTU energy per unit volume as 100% gas. That 3% fewer BTU, assuming a 33% efficiency in a combustion engine in converting thermal energy into mechanical energy, yields about 1% less mechanical energy. 1% of 556hp is 5.5hp. Not noticeable by seat of the pants but probably detectable on a dyno given everything else equal.

Now that 5.5hp loss is offset by any gain in advanced timing (or higher compression) allowed by the higher octane. If the octane has no benefit to our engines with max performance parameters already at 93 octane then it is truly a net loss to use Ultra94 due to the ethanol blend. If there is an advantage to the 94 octane level then the lower energy content is surely more than offset.
 
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