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Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, Octane and the 3.6 V6... in Cadillac SRX Forums; I've been wondering the same thing. I stopped using the 87 a couple of months ago in mine. I've been ...
  1. #16
    twenspirited is offline Cadillac Owners Member
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    Re: Octane and the 3.6 V6...

    I've been wondering the same thing. I stopped using the 87 a couple of months ago in mine. I've been using 89 and the engine sounds different when I accelerate to me. So I've just been sticking with 89.

  2. #17
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    Re: Octane and the 3.6 V6...

    I'm driving an 07 and I began using prieum grade as my dad demanded I use 93 because "it's a Cadillac". Well It preformed 'normal' to me. Fastforward a few months. I had my daughter pump the gas and she used 87. I was scared as my dad had told me that 87 would make the engine knock until it's gone. Well not true....the gas actually lasted longer. I drive 26 miles a day. I filled up on Sunday evening, yesterday only a quarter of the gas was used.

    I'm new to driving a Cadillac(purchased on Feb 28th) so my preception of this could be way off.

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    The ECU has no idea what octane is in the tank, it won't optimize any parameters based on what's in the tank or running through the fuel system.

    Timing (which is dynamic to begin with) will ONLY be pulled back IF knock is detected, which would only happen under higher load/RPM/throttle angles. Driving around normally, and under normal to moderate acceleration, there's essentially no chance of knock, and the engine functions identically with any octane fuel. 87-110 race fuel. If you're going to tow up a mountain or go to the drag strip, sure, use mid grade or premium if you want, but there'll be no noticeable difference. To actually feel any power gain, it has to be ~10% of the engines output.

    And no, there is NO change in how the engine sounds between octanes...

    Want to play "spot the difference" with timing? Look into a ScanGauge II.
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    Re: Octane and the 3.6 V6...

    With the DI engines from 2008-2011 the Bosch ECU is constantly adjusting for octane and park knock. So the result show up pretty quick. The 2012 and above with the Delphi PCM have a igh and low octane table so it will default to the low octane if detonation (knock) is detected a certain amount of times so it will take a certain amount of start/run cycles to try the high octane tables or a fuse pull or negative cable on the battery disconnected to allow reset.

    Knock any tuner that logs can verify what happens and in the end, the added cost of 93 vs 87 is about a wash for the increased MPG you would see in testing done. The power increase is nice, but again, this is ONLY on the DI versions. The port injection LY7 will be a waste of $ to run anything but 87 with the compression ratio it has.....but it IS critical to run top tire detergent fuels (Shell, etc.) to ensure the valves stay clean where the DI engines no fuel ever touches the valves so that is a waste of $. Run any brand fuel as all comes from the same bulk tanks and refineries. The additives are added later and they do nothing for any part of a DI's system.
    RX Performance Products/RevXtreme.com 941-721-1826

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    Re: Octane and the 3.6 V6...

    Quote Originally Posted by SC2150 View Post
    With the DI engines from 2008-2011 the Bosch ECU is constantly adjusting for octane and park knock. So the result show up pretty quick. The 2012 and above with the Delphi PCM have a igh and low octane table so it will default to the low octane if detonation (knock) is detected a certain amount of times so it will take a certain amount of start/run cycles to try the high octane tables or a fuse pull or negative cable on the battery disconnected to allow reset.

    Knock any tuner that logs can verify what happens and in the end, the added cost of 93 vs 87 is about a wash for the increased MPG you would see in testing done. The power increase is nice, but again, this is ONLY on the DI versions. The port injection LY7 will be a waste of $ to run anything but 87 with the compression ratio it has.....but it IS critical to run top tire detergent fuels (Shell, etc.) to ensure the valves stay clean where the DI engines no fuel ever touches the valves so that is a waste of $. Run any brand fuel as all comes from the same bulk tanks and refineries. The additives are added later and they do nothing for any part of a DI's system.

    I'm currently using WaWa (in Florida). How can I find out if their fuel is 'top tire detergent'? I have no idea what this means exactly but I gather is cleaner fuel, correct?

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    Re: Octane and the 3.6 V6...

    There are some websites that give guides...

    Here is one:

    http://www.toptiergas.com/retailers.html
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  7. #22
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    Re: Octane and the 3.6 V6...

    So I get that some of you are trying to be funny...some of you have no experience with what I asked but strong opinions about things and feel it needs to be shared and still others must not have read what I asked and clarified at least twice as you continue to bring up Premium fuel which had nothing to do with my request or this thread...

    I guess the writers of the Owner's Manual must just have been having a bit of fun when saying that performance might increase with 89 octane fuel...

    Thanks for your responses...

    Bill

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    Quote Originally Posted by silversport
    I have read several threads from a reliable source that using Mid Grade 89 octane in the 3.6 yielded positive results...this source had said he used the optional higher octane gasoline and got somewhat better performancel
    Unless the "source" dynod the vehicle, he'd have no idea if there was a performance difference. Any potential gain would be much too little to feel.

    [/QUOTE]somewhat better fuel economy (higher numbers)[/QUOTE]If he backed it up with logs of traveling the same roads, same temp, same speed, and same load, and observed a higher AVG MPG readout, great. If not, then no.

    Here's an idea, fill up with 89 next time. If YOU THINK it makes a difference in power or economy, or it just makes you feel warm and fuzzy inside, keep buying 89.

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    Re: Octane and the 3.6 V6...

    If we all did stuff like that, why would we need a Forum???

    Bill

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    Quote Originally Posted by conedoctor View Post

    Explain
    The way the ecu is mapped with the fuel tables on 87 and tuned to 87 the ecu wouldn't know how to compensate with the extra octane therefore wouldn't know what to do as far as making a different timing and fuel map for the increased octane is what I meant.

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    Umm, octane has NOTHING to do with air/fuel ratio.

    Running 93 in an engine designed for a lower octane requires exactly no compensating. There is nothing different about it other than its resistance to detonate under the heat of compression, and the engine/PCM doesn't have a clue what's in the tank.

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    Re: Octane and the 3.6 V6...

    so with the engine running close to spark knock and the ECM advancing or retarding timing to compensate, you don't believe the slightly higher ability to prevent spark knock of the Mid Grade might give the engine slightly higher performance and gas mileage???...I'm just asking the question...if not...why does the Owner's Manual mention to try Mid Grade (not Premium) for higher performance and mileage???...

    Bill

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    Re: Octane and the 3.6 V6...

    Quote Originally Posted by silversport View Post
    So I get that some of you are trying to be funny...some of you have no experience with what I asked but strong opinions about things and feel it needs to be shared and still others must not have read what I asked and clarified at least twice as you continue to bring up Premium fuel which had nothing to do with my request or this thread...

    I guess the writers of the Owner's Manual must just have been having a bit of fun when saying that performance might increase with 89 octane fuel...

    Thanks for your responses...

    Bill
    Hi Bill, The forums are great places to gather, share passions, and learn/share info. But you are correct that it gets confusing because so many that are not automotive engineers or techs that do build these will come in and offer their "opinion". Most mean well and feel strongly because they read, know someone, or know someone that knows someone that heard that....and there is where confusing viewpoints collide.

    I share over 40 years of working on the tech and engineering side of the automotive industry. I started as a GM tech in 1974 and really began focusing on the direct injection engines in 2008 designing performance products for them, with the GM DI engines as a focus. What I share is from the engineering side, logging and dyno testing, etc. So if you have a specific question you get conflicting info on, you can always PM me and I will either give you accurate confirmed info w/data to support it, or tell you I don't know.

    Hope this helps.

    ----------

    Quote Originally Posted by silversport View Post
    so with the engine running close to spark knock and the ECM advancing or retarding timing to compensate, you don't believe the slightly higher ability to prevent spark knock of the Mid Grade might give the engine slightly higher performance and gas mileage???...I'm just asking the question...if not...why does the Owner's Manual mention to try Mid Grade (not Premium) for higher performance and mileage???...

    Bill
    Yes it will as long as itis a DI version of the engine (most 2008 and up). We and most other tuners see it in the knock retard logged and our testing. But be aware if you have 15-20k miles or more, the amount of intake valve coking will negate most due to the obstructed ports and valves:

    Here is what your valves probably look like:



    This has a negative effect on the efficiency of the flow into the cylinder.

    After a manual cleaning, it looks like this:
    RX Performance Products/RevXtreme.com 941-721-1826

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    Re: Octane and the 3.6 V6...

    SC2150...thanks and I gathered from your posts now and in the past that you came from the engineering side...my 2008 SRX doesn't have a Direct Injection motor (unless I'm mistaken) ...I'll do my own experiment and decide on my own...I figured the 3.6 engine had been out long enough and that this ground would already have been tread by now...it has been on another Forum and I have learned from other responses to trust some of the people there too from their background...

    If I tried Mid Grade gasoline and saw a couple MPG increase and similar HP (because performance is much more than just power) with little to no downside, I might make the switch...if it is as I suspect on my motor, more internet myth...I'll pass...

    I really do appreciate all the responses...I find it a blueprint to others knowledge, experience and sometimes, agenda...

    Bill

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    Quote Originally Posted by silversport View Post
    SC2150...thanks and I gathered from your posts now and in the past that you came from the engineering side...my 2008 SRX doesn't have a Direct Injection motor (unless I'm mistaken) ...I'll do my own experiment and decide on my own...I figured the 3.6 engine had been out long enough and that this ground would already have been tread by now...it has been on another Forum and I have learned from other responses to trust some of the people there too from their background...

    If I tried Mid Grade gasoline and saw a couple MPG increase and similar HP (because performance is much more than just power) with little to no downside, I might make the switch...if it is as I suspect on my motor, more internet myth...I'll pass...

    I really do appreciate all the responses...I find it a blueprint to others knowledge, experience and sometimes, agenda...

    Bill
    What was your gas mileage before and after and we're they under the EXACT same driving conditions, traffic and weather? Also how can you tell the hp increase without a serious increase in power? I'm pretty sure the slight increase is a placebo effect and you "think" you are getting more power remember butt dyno doesn't count. ?

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