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2008-2013 Cadillac CTS General Discussion Discussion, Ethanol Free Gas location link in Cadillac CTS Second Generation Forum - 2008-2013; https://www.pure-gas.org/ After wondering about it long enough I finally tried to find some ethanol free gas and discovered it's right ...
  1. #1
    Joseph Upson is offline Cadillac Owners Enthusiast
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    Ethanol Free Gas location link

    https://www.pure-gas.org/

    After wondering about it long enough I finally tried to find some ethanol free gas and discovered it's right up the street from me two blocks away at the new WAWA, which appears to be one of the most common supply sources offering it in 89 octane, at the pumps with the baby blue color code on the tag high above and at the pump handle.

    I put 7 gallons in on top of the ~3 gal of 10% to see if there would be a noticeable difference.

    To put things in context, I managed a best of 30 mpg hwy on the 80 mile leg too my Mom's house before the intake valve cleaning on premium and a 29.7 mile best on the way back after the intake valve cleaning on 89 octane, but during a different round trip than the preceding measure.

    Two of the latest round trips were down by about 1.5-2 miles going and returning after the valve cleaning job. I suspected a possible change in the fuel mix. The 30 mpg best was on premium fuel before the valves were cleaned at ~80 F and the best return trip 29.7 after the valve cleaning on 89, with ethanol mix and ~72 deg ambient, as well as the two reduced expectation trips.

    I took the trip to test the fuel this morning at about 74 F and managed about 28.8 mpg hwy, still down 1 mpg, leading me to dismiss the likelihood of any improvement. The trip back netted the best mpg hwy on the return that I have ever seen from the car on this route, 30.9 mpg hwy at the light after taking the exit at the end of the route and 29.5 when I parked after 2.5 miles of surface streets. I'm going to round it to 31, because of ~3 miles of stop and go slow traffic on 70 mph I-4, which broke my 30+ mpg stride average at the onset and the fact the fuel in the tank was not 100% gasoline having an estimated 1.5% ethanol remaining by dilution from mixing. Previously, the last 10 or so miles of the trip would be hammered by the hills on the toll road, but this time efficiency held pretty steady, changing slowly and slightly.

    The initial lack of change in economy may have been influenced by the fact the car was driven back home 2 blocks and parked before being put on the interstate after the ethanol free gas was added and the PCM needed time to detect and adjust to take advantage of the fuel change during the trip. I understand the owners manual states the best performance can only be had with use of premium fuel so chances are pretty good, that premium fuel has a similar effect efficiency wise that 100% gasoline has to an extent, where premium is capable of greater spark advance for improved efficiency and ethanol free 89 just has more energy content in the absence of increased spark advance.

    The computer can easily with programming be setup to detect fuel quality without dedicated sensors by comparing engine load changes in steady state against fuel demand and response to changes in spark advance, which it probably is. Obviously the higher energy content of 100% gasoline, requires less throttle input to maintain the same conditions of E10-15. That's another thing to be aware of, some pumps say 10% ethanol and I believe I have seen some read "not less than 10%", or something of that sort to suggest the potential to get a little more than 10%, that being as high as 15%. It's also possible I may have gotten a hold of 100% 89 octane before and didn't know it, as I also believe I have seen pumps read "Up to 10% ethanol".

    I'll keep going with the 100% and be on the lookout for more definitive proof.
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    Submariner409's Avatar
    Submariner409 is offline If it won't run, install a sound system
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    Re: Ethanol Free Gas location link

    I did the same sort of ethanol/no ethanol tests during two 1750 mile round trips to Florida and back - straight gas one way, E10 the other. Royal PITA to find non-ethanol stations within short distances of I-95. Pricing for the straight gas was scary expensive so NO economy there.

    No differences in either fuel mileage or performance. The 2002.5 STS.

    pure-gas.org has been posted on and off down in the Engines and Lounge forums since about 2006. I may still have some reports for MD in there somewhere.

  4. #3
    jayoldschool's Avatar
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    Re: Ethanol Free Gas location link

    I can only get 91 no ethanol here. I run that in everything with a carb, along with one FI car that is programmed for it. The cost difference isn't worth it to run in the CTS.

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    Joseph Upson is offline Cadillac Owners Enthusiast
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    Re: Ethanol Free Gas location link

    With the price markup the improvement I'm seeing so far if consistent will pretty much be at the break even point, where as with everything that lasts longer, or gives you more for your money, there will be some sort of symbolic taxation attached to keep the ratio the same. I imagine the ethanol free is for people like jayoldschool who needs to protect his carbs from the alky. I remember running rubbing alcohol in my gokart motor one time, because that's all it took to ruin the aluminum carb.

    E10 offers an octane boost advantage that I generally prefer, particularly during the Summer.

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    Re: Ethanol Free Gas location link

    Agree with the octane boost from ethanol but that is mitigated by being mixed with about 85 PON gas to get 87. Cheaper gas plus subsidized alky means a lower wholesale price than pure dino.

    BTW it is not the carbs that need protection but the rubber seals and diaphrams. Nitrile seals have been available since the '70s. Ask Jon at the Carb Shop.


    And just to be annoying, "where premium is capable of greater spark advance for improved efficiency " errrr No. The higher the octane the slower it burns (flame propagation rate) so premium MUST have more advance than regular. Both regular and premium gasoline have the same "power" (btu/gal) just the slower burning "premium" is less likely to detonate at higher compression ratios, something greatly mitigated by direct injection, why diesels (CI engines) use it.

    Once upon a time in the last century I (and many others) thought that turbo diesels with DI was the next big thing but then GM destroyed the passenger car market in the US until after the turn of the century. Now Politics are pricing diesel out of the consumer market. Could be that the US just does not want diesel cars.

    Meanwhile back at the CTS if DI is so great why is my mpg so bad ? May be because DI works best with boost. This is why the '19 Hyundai Turbo Veloster can make 135 hp/liter. In production trim. With a warranty. Has been for a few years. That would be 486 hp from a 3.6 (sound like an ATS-V ?). So is kind wasted on a 300hp V-6 (see Pentastar for a similar engine without DI and better mpg).

    But for now I am just removing a lot of the non-functional bling from my CTS-C and transforming it into the great road car it can be. Jury is still out on the 3.73 though but changing would require a reprogrammed ABS module.

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    Joseph Upson is offline Cadillac Owners Enthusiast
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    Re: Ethanol Free Gas location link

    Quote Originally Posted by Padgett View Post
    ...And just to be annoying, "where premium is capable of greater spark advance for improved efficiency " errrr No. The higher the octane the slower it burns (flame propagation rate) so premium MUST have more advance than regular. Both regular and premium gasoline have the same "power" (btu/gal) just the slower burning "premium" is less likely to detonate at higher compression ratios, something greatly mitigated by direct injection, why diesels (CI engines) use it.

    Once upon a time in the last century I (and many others) thought that turbo diesels with DI was the next big thing but then GM destroyed the passenger car market in the US until after the turn of the century. Now Politics are pricing diesel out of the consumer market. Could be that the US just does not want diesel cars.

    Meanwhile back at the CTS if DI is so great why is my mpg so bad ? May be because DI works best with boost. This is why the '19 Hyundai Turbo Veloster can make 135 hp/liter. In production trim. With a warranty. Has been for a few years. That would be 486 hp from a 3.6 (sound like an ATS-V ?). So is kind wasted on a 300hp V-6 (see Pentastar for a similar engine without DI and better mpg).

    But for now I am just removing a lot of the non-functional bling from my CTS-C and transforming it into the great road car it can be. Jury is still out on the 3.73 though but changing would require a reprogrammed ABS module.
    Not annoying at all. Let me clarify, I'm speaking within this 3.6L system, in order for GM to make the claim that this motor delivers its greatest performance on premium fuel, one would have to conclude that premium fuel delivers/supports an efficiency level higher than fuels of lower octane rating can deliver.

    The higher the compression ratio on a given motor, the greater its efficiency. With that said, we must also assume that GM delivered this platform to the public, under tuned to less than the maximum productive spark angle that it is capable of on premium fuel, in which case advancing the timing further which the premium fuel would allow, should deliver even greater efficiency, even if it is a small amount. If that is not the case, then all of these so called performance tunes being sold to the public claiming performance gains are a big fat ..., because GM has already tuned it to its maximum and one simply only needs to run premium fuel only to enjoy it. If they haven't, then moving from 89, to 92, restores efficiency by enabling existing greater spark advance.


    My statement was not to suggest you can get better efficiency from a motor that doesn't have it, by simply adding higher octane. I understand that premium burns slower than lower grade fuels and is more stable, and some times I skip minor details when I know those reading for the most part are aware of them. From a description of the complicated BOSCH PCM programming, as described by someone with a good bit of experience tuning it, the PCM doesn't just go to a box on a spark table and pick and apply that degree of advance. It appears to be an adaptive process, where within the limits, the apparent best value for conditions is chosen.

    If the CTS' PCM does not have adaptive ability to take advantage of premium fuel in a car rated for 87 octane, it would make absolutely no sense to use it and GM would have libeled themselves by suggesting it.

    DI is so great because you're running 11.5:1 compression ratio on 87 octane wideopen, pedal to the floor without a care. Pull that stunt on the same motor port injected, successfully with no other changes except what's necessary for proper fuel delivery and then you can shake a finger at DI. You have what GM has offered, not what DI is maximally capable of on a naturally aspirated motor. I'm confident the compression ratio could be run higher than that without a problem.

    Your fuel economy is the pits partly if not mostly because you have a 3.73 rear end behind a transmission with a 4.06 first gear and 2.37 second, it's hard to save much more than time going from 0 to 60 with that combo.

    There's also a lot below the surface we often are not aware of about our cars from the manufacturer. You may have a factory tune that sacrifices more fuel efficiency than others for greater performance.

  8. #7
    DavesWagon's Avatar
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    Re: Ethanol Free Gas location link

    according to the site, the only places within a reasonable distance to me are airports and race shops and most only have 100 octane. The closest one with 91 is an hour away and won't pump directly into the car, I'd have to bring a can. It was something like $7/gallon too.

    FWIW, my 2011 owners manual does NOT mention any performance gains from using higher than 87 for any of the V6's, only the V8. I know they did recommend for the earlier years, but not 2011+:

    Recommended Fuel
    If the vehicle has a V6 engine,
    use regular unleaded gasoline with
    a posted octane rating of 87 or
    higher. If the octane rating is less
    than 87, an audible knocking noise,
    commonly referred to as spark
    knock, might be heard when driving.
    If this occurs, use a gasoline rated
    at 87 octane or higher as soon as
    possible. If heavy knocking is heard
    when using gasoline rated at
    87 octane or higher, the engine
    needs service.

    If the vehicle has the 6.2L V8 engine
    (VIN Code P), use premium
    unleaded gasoline with a posted
    octane rating of 91 or higher. For
    best performance, use premium
    unleaded gasoline with a posted
    octane rating of 93. In an
    emergency, you can use regular
    unleaded gasoline with an octane
    rating of 87 or higher. If 87 octane
    fuel is used, do not perform any
    aggressive driving maneuvers such
    as wide open throttle applications.
    silversport likes this.

  9. #8
    Padgett's Avatar
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    Re: Ethanol Free Gas location link

    Agree with the octane boost from ethanol but that is mitigated by being mixed with about 85 PON gas to get 87. Cheaper gas plus subsidized alky means a lower wholesale price than pure dino.

    BTW it is not the carbs that need protection but the rubber seals and diaphrams. Nitrile seals have been available since the '70s. Ask Jon at the Carb Shop.


    And just to be annoying, "where premium is capable of greater spark advance for improved efficiency " errrr No. The higher the octane the slower it burns (flame propagation rate) so premium MUST have more advance than regular. Both regular and premium gasoline have the same "power" (btu/gal) just the slower burning "premium" is less likely to detonate at higher compression ratios, something greatly mitigated by direct injection, why diesels (CI engines) use it. The DI is probably why there is no gain to using premium (or anything more than 87 PON (85 in Denver)).

    Once upon a time in the last century I (and many others) thought that turbo diesels with DI was the next big thing but then GM destroyed the passenger car market in the US until after the turn of the century. Now Politics are pricing diesel out of the consumer market. Could be that the US just does not want diesel cars.

    Meanwhile back at the CTS if DI is so great why is my mpg so bad ? May be because DI works best with boost. This is why the '19 Hyundai Turbo Veloster can make 135 hp/liter. In production trim. With a warranty. Has been for a few years. That would be 486 hp from a 3.6 (sound like an ATS-V ?). So is kind wasted on a 300hp V-6 (see Pentastar for a similar engine without DI and better mpg).

    But for now I am just removing a lot of the non-functional bling from my CTS-C and transforming it into the great road car it can be. Jury is still out on the 3.73 though but changing would require a reprogrammed ABS module.

  10. #9
    silversport's Avatar
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    Re: Ethanol Free Gas location link

    I think the use of higher octane fuel for the CTS has changed throughout the production years of the 2nd ten CTS...my 2014 Sportwagon owner's manual is similar to the one DavesWagon posted for his 2011...

    did Padgett just quote himself???

    Bill

  11. #10
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    Re: Ethanol Free Gas location link

    No, I quoted Joseph. And yes, the recommendation would be different before and after DI. That eliminates the kludges in place since the last century to avoid detonation. (have I mentioned "Maximum Cylinder Pressure" & the "sweet spot" ?)

  12. #11
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    Re: Ethanol Free Gas location link

    The 2010 CTS manual agrees with what DavesWagon posted about fuel octane rating. Anything over 87 is a waste for the 3.6L.

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    Re: Ethanol Free Gas location link

    Quote Originally Posted by Padgett View Post
    No, I quoted Joseph. And yes, the recommendation would be different before and after DI. That eliminates the kludges in place since the last century to avoid detonation. (have I mentioned "Maximum Cylinder Pressure" & the "sweet spot" ?)
    if you click the "Quote" button, it will format the quoted text differently so it's much easier to see the quoted text vs. your response.

    Wasn't the 2008 3.6L DI too though?
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  14. #13
    Joseph Upson is offline Cadillac Owners Enthusiast
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    Re: Ethanol Free Gas location link

    Quote Originally Posted by Padgett View Post
    Agree with the octane boost from ethanol but that is mitigated by being mixed with about 85 PON gas to get 87. Cheaper gas plus subsidized alky means a lower wholesale price than pure dino.

    BTW it is not the carbs that need protection but the rubber seals and diaphrams. Nitrile seals have been available since the '70s. Ask Jon at the Carb Shop.


    And just to be annoying, "where premium is capable of greater spark advance for improved efficiency " errrr No. The higher the octane the slower it burns (flame propagation rate) so premium MUST have more advance than regular. Both regular and premium gasoline have the same "power" (btu/gal) just the slower burning "premium" is less likely to detonate at higher compression ratios, something greatly mitigated by direct injection, why diesels (CI engines) use it. The DI is probably why there is no gain to using premium (or anything more than 87 PON (85 in Denver)).

    Once upon a time in the last century I (and many others) thought that turbo diesels with DI was the next big thing but then GM destroyed the passenger car market in the US until after the turn of the century. Now Politics are pricing diesel out of the consumer market. Could be that the US just does not want diesel cars.

    Meanwhile back at the CTS if DI is so great why is my mpg so bad ? May be because DI works best with boost. This is why the '19 Hyundai Turbo Veloster can make 135 hp/liter. In production trim. With a warranty. Has been for a few years. That would be 486 hp from a 3.6 (sound like an ATS-V ?). So is kind wasted on a 300hp V-6 (see Pentastar for a similar engine without DI and better mpg).

    But for now I am just removing a lot of the non-functional bling from my CTS-C and transforming it into the great road car it can be. Jury is still out on the 3.73 though but changing would require a reprogrammed ABS module.
    I'm aware that premium burns slower, and had actually posted a bit more to clarify my statement in regards to varying engine efficiency vs. the octane rating of the fuel used, but I must have stepped on the proverbial toes of some entity given a statement, or two I made that may have resulted in the post getting "lost", no harm intended.

    ' "where premium is capable of greater spark advance for improved efficiency " errrr No. The higher the octane the slower it burns (flame propagation rate) so premium MUST have more advance than regular.'.

    Compression ratio dictates the fuel, so a motor may require premium fuel to run the max advance it is capable of within its programming, but putting premium in a motor that does not require it and raising spark advance to justify it, is a theory that wouldn't work in a low compression motor except to make matters worse, so premium must have more compression, as you can already be at the limit for maximal spark advance in a given motor with no more room to advance spark.

    Thanks to a recall victory with my memory, although mid grade and premium would better reduce the chance of spark knock, the car should be capable of generating its specified power output on 87 octane, because the EPA requires cars to be sold with recommendations for the same fluids used to spec it. Perhaps there's a mix up in the manuals sourced, that has given rise to the premium suggestion for better performance, or it is relevant to certain years .

    2008 and 2009 have a number of specifics that changed between the two and for 2010-up. None should require anything more than 87 octane, but I know without question my motor ran better on premium than on 87. I noted a significant change for the better in that notorious flat spot during mild acceleration that many have complained about, among other things.

  15. #14
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    Re: Ethanol Free Gas location link

    While I'm certain that your engine ran better on premium than on 87 regular, your wallet was running flat out.

  16. #15
    Joseph Upson is offline Cadillac Owners Enthusiast
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    Re: Ethanol Free Gas location link

    Quote Originally Posted by tinman View Post
    While I'm certain that your engine ran better on premium than on 87 regular, your wallet was running flat out.
    I don't drive enough at the moment for it to be noticed and at a difference of only about $3-4 a tank, I can cut back on my love for bacon to offset it. I might have to do that anyway since the pigs in China are getting scary sick and you know what that means for prices.

    I just checked my owners manual and found the culprit. First, it is alluded to in the manual that a move to 89 octane may be appropriate for some, in the event that spark knock/ping is noted on 87 octane. The actual statement regarding best performance, on 89 as opposed to premium is in reference to the LY7, which saw its last year in the CTS in 09. So if the info is missing from 2010 and later manuals, that would be why.
    tinman and silversport like this.

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