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2009-2014 Cadillac CTS-V General Discussion Discussion, Octane Question in Cadillac CTS-V Series Forum - 2009-2014; Only one station in town has 93+ and that is Chevron. All the others the best is 91. Any issue ...
  1. #1
    brian-nicola is offline Cadillac Owners Fanatic
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    Octane Question

    Only one station in town has 93+ and that is Chevron. All the others the best is 91. Any issue do you think with 91? (normal city driving of course) 93+ for stomp and steer w'end drives....

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    cruiser68 is offline Cadillac Owners Enthusiast
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    Re: Octane Question

    No issue. In higher elevations you don't get better than 91. Worst case it will retard timing if it starts knocking.

  4. #3
    Smokin_Cache is offline Cadillac Owners Member
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    Re: Octane Question

    I feel like I am getting ripped off when I travel to a state that sells 91 at the price we get 93 for. I remember traveling through a state somewhere that had 5 octane selections at the pump. Can't remember where. The 76 stations use to have a pump with 100 on the east coast. That was when the had the NASCAR contract.

  5. #4
    Trapspeed's Avatar
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    Re: Octane Question

    100 octane is such a great thing. Love that stuff.

  6. #5
    brian-nicola is offline Cadillac Owners Fanatic
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    Re: Octane Question

    Thanks for the repies...I remember SONOCO 100 octane. Now you have to go to the airport for AV100
    Here in British Columbia 91 is 1.48/Ltr = 5.62 per US Gallon

  7. #6
    GMX322V S/C's Avatar
    GMX322V S/C is offline Cadillac Owners Connoisseur
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    Our motors are designed to run on 91 R+M/2. Anything beyond that would be a hedge against pulling timing under extreme conditions, but the motor will protect itself just fine on 91 regardless.

    100 is also available at selected 76 stations here in SoCal. Regarding AvGas, if it's leaded, it'll poison your cats if you're running them.

  8. #7
    V locity's Avatar
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    Re: Octane Question

    Plus, if you're timing's not tuned to the 100, not really any upside...

  9. #8
    Fireverm is offline Cadillac Owners Fanatic
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    Re: Octane Question

    Quote Originally Posted by Smokin_Cache View Post
    I feel like I am getting ripped off when I travel to a state that sells 91 at the price we get 93 for. I remember traveling through a state somewhere that had 5 octane selections at the pump. Can't remember where. The 76 stations use to have a pump with 100 on the east coast. That was when the had the NASCAR contract.
    You are aware that 91 octane has more "gas" in it than 93 right? Refined gasoline starts out at a low octane and then is diluted with crap that doesn't burn to raise the octane of it so it can be compressed more before spontaneously exploding. You can take 87 octane and inject water to give you 110 octane if you wanted. All of those "additives" they put in premium gasoline are marketing nonsense, it doesn't make the gasoline more powerful, it actually makes it less powerful by volume. However, the benefit of higher octane is that you can compress it more before it explodes, so even though it is less powerful fuel per volume, you make up the difference and then some if you are compressing it more.

    But your vehicle needs to take advantage of that fact. If your vehicle is designed to be able to run 91, in almost all situations, running 100 octane will in fact make less power unless you are able to increase the cylinder pressure either by adding more boost in a forced induction setup (like ours) or by changing the heads or pistons to give more compression.

    Bottom line, if your car is setup to run 91, it will make less power and be slower running higher octane than specified unless your car is specifically configured to take advantage of higher octane.

  10. #9
    tedcmiller is offline Cadillac Owners Connoisseur
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    Re: Octane Question

    The CTS-V is specified for 91 octane minimum. Where I live the only octanes available are 89 and 93, so I go with 93 to meet the minimum spec.. If the car is unmodified it should run fine on 91 octane. Anything over 91 octane (if the car runs OK) is a waste (for normal street driving or the track). Those people who think 100 octane is wonderful (for stock CTS-Vs) are kidding themselves. The same goes for my motorcycles (2008 and 2012 H-Ds).

  11. #10
    Pphilthy's Avatar
    Pphilthy is offline Cadillac Owners Fanatic
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    Running 100 octane will make your car less powerful...? lol - these cars are developed to run a minimum of 91 from the factory, but it will make more on 100 octane, not less... Most ECU's are designed to pull and add timing based on dynamic advance tables that are enabled based on certain criteria, air intake temps, knock, exhaust has temps, etc... The bases of your post is technically correct given all things equal, but not applicable in a boosted car with modern ECU capabilities... Running higher octane fuel than the minimum required 91 will place your ECU in the happy zone and allow it to run full programmed timing = more power and for longer because of the added cooling effect of the higher, slower burning fuel...

    Also, higher octane fuel isn't made by just adding water, haha. Go ahead and try that on your car and let us know how it works out for you... There's a reason why fuel companies use octane boosters with nitrogen carriers. Most use methanol, isopropyl alcohol, naptha, xylene, toluene), benzine, hexane, nitro benzine, aniline, etc., but they never tell you exactly what or how much they use - its called trade secrets... Those additives they add to the fuel do a lot to combat all of the negative effects of running unleaded fuel, such as varnish and deposit build up, storage life, reaction to oil, etc... These aren't issues with leaded fuel but are with unleaded...

    Granted, you will make much more power by tuning your car to optimize the timing for the higher octane... But there is no way you'll make less HP - the statement is true if you run lower octane as the ECU will pull timing and will run much hotter....

  12. #11
    Fireverm is offline Cadillac Owners Fanatic
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    Re: Octane Question

    Quote Originally Posted by Pphilthy View Post
    Running 100 octane will make your car less powerful...? lol - these cars are developed to run a minimum of 91 from the factory, but it will make more on 100 octane, not less... Most ECU's are designed to pull and add timing based on dynamic advance tables that are enabled based on certain criteria, air intake temps, knock, exhaust has temps, etc... The bases of your post is technically correct given all things equal, but not applicable in a boosted car with modern ECU capabilities... Running higher octane fuel than the minimum required 91 will place your ECU in the happy zone and allow it to run full programmed timing = more power and for longer because of the added cooling effect of the higher, slower burning fuel...


    Also, higher octane fuel isn't made by just adding water, haha. Go ahead and try that on your car and let us know how it works out for you... There's a reason why fuel companies use octane boosters with nitrogen carriers. Most use methanol, isopropyl alcohol, naptha, xylene, toluene), benzine, hexane, nitro benzine, aniline, etc., but they never tell you exactly what or how much they use - its called trade secrets... Those additives they add to the fuel do a lot to combat all of the negative effects of running unleaded fuel, such as varnish and deposit build up, storage life, reaction to oil, etc... These aren't issues with leaded fuel but are with unleaded...


    Granted, you will make much more power by tuning your car to optimize the timing for the higher octane... But there is no way you'll make less HP - the statement is true if you run lower octane as the ECU will pull timing and will run much hotter....

    I emphatically disagree with several of your points.


    These cars in stock trim will certainly make less power on 100 octane than 91. Now I'll grant you that you might be able to come up with a scenario where this is not the case, like where the IATs are so high it is pulling obscene timing while using 91...like....let's say if you are doing the dyno run out in the sun in Death Valley in July. And in that situation, the power output will be substantially reduced in either case so who cares.


    In standard temps and pressures the ecu may not pull much timing, if any at all, while running 91 under high load. It's not like they designed this powerplant to run super inefficiently on even the highest octane pump gas available nationwide and that there is a ton of timing overhead that can be tapped into. I can just hear that conversation now, "Hey somebody tell the powerplant engineers that I want a new platform based on a 6.2 liter LS block. Tell them I want forced induction, preferably supercharged. Tell them I want it called LSA. Oh, and one more thing....tell them to design it to run most efficiently on 100 octane and then for the actual production run we'll just retard the **** out of the timing so the customers can run it on 91."


    As temps rise, the ecu will certainly adjust timing depending on the load, but there is only so much you can do with timing. The adjusting that the ecu will do with the timing is an attempt to try to minimize the loss of power from your theoretical maximum, not primarily as a power adder above and beyond. If what you were saying is right, then why would anyone run forced induction when we can make shit loads of power just by running high octane gas and advancing the timing?


    100 octane has lower specific energy per volume than 91 and the only way to really make that loss up is by increasing the compression, which in stock trim isn't happening just because modern day ecus are magic.


    Also, I didn't say that higher octane gasoline is made just by adding water. I stated that you could effectively increase your octane by injecting water into the combustion chamber, as many race cars have done. If you don't believe me, science and google are your friend. The additives they put in are non-combustible compounds that dilute your gasoline and decrease it's specific energy so you can compress it more before it explodes. Many compounds will work, there is nothing special about the blends of bullshit the petroleum companies put in there if all you are trying to do is raise the octane. And that's why initially we turned to leaded fuel, it was added to the gasoline to increase it's octane rating by lowering the specific energy of the fuel.


    So back to my bottom line, in stock trim you will make less power running 100 octane over 91 unless your normal stomping grounds are on the day side of Mercury.
    V locity and V locity like this.

  13. #12
    V locity's Avatar
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    Re: Octane Question

    ^^^ Nice siphering Fireverm! Gasoline has the same BTU's or thermal conversion regardless of burn rate (octane). So if you want more power, at the same compression, you need more fuel & oxygen. There are additives for gasoline like say Propylene Oxide that would allow you to richen the mixture to a small extent & hence get more power.

    More commonly though, we see NOS. Oxygen spray with more (gasoline of the same octane). The amount of power these systems produce is only limited to how much your motor can handle.

    Then, there's the old trick, for those in the know, of going down to the local Sherwin Williams

  14. #13
    GMX322V S/C's Avatar
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    Toluene?

  15. #14
    Tampa2Dubai is offline Cadillac Owners Member
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    Re: Octane Question

    Quote Originally Posted by Fireverm View Post
    I emphatically disagree with several of your points.


    These cars in stock trim will certainly make less power on 100 octane than 91. Now I'll grant you that you might be able to come up with a scenario where this is not the case, like where the IATs are so high it is pulling obscene timing while using 91...like....let's say if you are doing the dyno run out in the sun in Death Valley in July. And in that situation, the power output will be substantially reduced in either case so who cares.


    In standard temps and pressures the ecu may not pull much timing, if any at all, while running 91 under high load. It's not like they designed this powerplant to run super inefficiently on even the highest octane pump gas available nationwide and that there is a ton of timing overhead that can be tapped into. I can just hear that conversation now, "Hey somebody tell the powerplant engineers that I want a new platform based on a 6.2 liter LS block. Tell them I want forced induction, preferably supercharged. Tell them I want it called LSA. Oh, and one more thing....tell them to design it to run most efficiently on 100 octane and then for the actual production run we'll just retard the **** out of the timing so the customers can run it on 91."


    As temps rise, the ecu will certainly adjust timing depending on the load, but there is only so much you can do with timing. The adjusting that the ecu will do with the timing is an attempt to try to minimize the loss of power from your theoretical maximum, not primarily as a power adder above and beyond. If what you were saying is right, then why would anyone run forced induction when we can make shit loads of power just by running high octane gas and advancing the timing?


    100 octane has lower specific energy per volume than 91 and the only way to really make that loss up is by increasing the compression, which in stock trim isn't happening just because modern day ecus are magic.


    Also, I didn't say that higher octane gasoline is made just by adding water. I stated that you could effectively increase your octane by injecting water into the combustion chamber, as many race cars have done. If you don't believe me, science and google are your friend. The additives they put in are non-combustible compounds that dilute your gasoline and decrease it's specific energy so you can compress it more before it explodes. Many compounds will work, there is nothing special about the blends of bullshit the petroleum companies put in there if all you are trying to do is raise the octane. And that's why initially we turned to leaded fuel, it was added to the gasoline to increase it's octane rating by lowering the specific energy of the fuel.


    So back to my bottom line, in stock trim you will make less power running 100 octane over 91 unless your normal stomping grounds are on the day side of Mercury.
    FYI .. european/export spec cts-v's are rated at 564bhp, due to running on 95-98 octane

    http://www.cadillaceurope.com/en/index.php#/cts-v-sedan

  16. #15
    V locity's Avatar
    V locity is offline Cadillac Owners Connoisseur
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    Re: Octane Question

    So then my wifes GS350 should make 556hp because it uses the same octane as the V?

    Look, I had a 13 hp difference on my base dyno runs last week, 1 minute apart & on the same fuel both pulls. I didn't change to a lower octane one minute later:

    http://www.cadillacforums.com/forums...ck-2011-a.html

    Once again, Gasoline, regardless of how fast you allow it to ignite, creates the same amount of energy or thermal conversion (heat).

    Maybe this will help... Diesel creates more power in the form of BTU's (thermal conversion) than the equivilant amount of gasoline, yet it's octane level is under 30% that of gas...

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