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Scangauge and octane

Discussion in '2nd Gen. Tacomas (2005-2015)' started by supralight, May 14, 2011.

  1. May 14, 2011 at 12:12 PM
    #1
    supralight

    supralight [OP] Well-Known Member

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    Anybody noticed this?:

    I've done the test quite a few times now. Using the "fillup" function on the scangauge, you have to trim your amount of fuel for the scangauge to be exact.

    When filling up with 91 octane, my % trim ALWAYS goes down a few percent 4-6%. Then, after a few tanks of 91 octane, when I switch back to 87 octane, during the next few tanks (1 to 3 tanks) I always have to adjust the trim back a few percentage points. That's the 3rd time I do the switch back and forth, and I always get this result.

    I run at least a few tanks of the same octane rating before switching.

    Also, with similar driving habits, I seem to get approximatly the same gain in fuel economy as my trim adjustement with the scangauge.

    Thoughts anyone? It would be great if anyone else could test and confirm this. Note: you have to run at least 3-4 tanks of the new octane to get full "effect" on the scangauge trim.
     
  2. May 14, 2011 at 12:35 PM
    #2
    j4x4ar3

    j4x4ar3 Well-Known Member

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    I've never had a problem with mine and I've used it for a couple years now. I run 89 and 91 in my truck depending on if I'm towing or not. As a daily driver the SG is always within .1 gallons of what I actually put in. Pretty darn accurate.

    The only "problem" I have is that when I go from towing to not towing in the same tank of gas the SG can be off as much as a gallon. Not sure why or how it calculates the amount of fuel remaining. I get 10mpg average and 20-24mpg when not towing.

    I also noted that the empty idiot light comes on with 4 gallons to spare using the SG. This is pretty accurate as well and I can almost tell you exactly when the light will come on by looking at the SG fuel till empty.
     
  3. May 14, 2011 at 1:36 PM
    #3
    supralight

    supralight [OP] Well-Known Member

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    Thanks for the infos. Maybe part of your difference is related to the octane rating, hence the change in calculated fuel consumed?

    Clarification: I was not pointing at a problem, but rather a possibility that our V6 engines are probably programmed to accept higher octane rating, which lead to a small increase in fuel economy (and power).
     
  4. May 15, 2011 at 1:25 AM
    #4
    808TRDTaco10

    808TRDTaco10 Black Sand Mirror

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    Interesting...so maybe I'm not wasting money on premium fuel after all...subscribed. :)
     
  5. May 16, 2011 at 9:40 PM
    #5
    j4x4ar3

    j4x4ar3 Well-Known Member

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    It's been talked about a bizillion times here in TW. The octane doesn't give you more power. The only thing the higher octane does for you is to allow your engine to function more efficiently. Lower octane fuel has a different flash point than higher octane fuel and can ignight prematurely causing your engine to knock. High compression engines can only further to cause lower octane fuel to ignight too soon. Toyota recomends premium fuel for best power and performance because in all high compression engines there are what is called knock sensors. When these sensors "hear" knocking they will retard the timing and reduce power to keep the fuel from ignighting too soon. Too much knock can damage and engine and is most common when under load such as hard acceleration, towing or carrying a lot of weight in the bed.

    When the sensors retard timing and such you get reduced HP and Torque from the engine and therefore a loss in power. By using high octane fuel you don't gain any additional power but only allow the engine to reach it's full potential by cutting out the knock. Premium fuel has a high flash point than regular and has additional additives to reduce the knock potential which is why premium fuel costs more. I find for me that using mid-grade as a daily driver eliminates the knock I've experienced with regular but when towing my 5500# trailer I need to use premium for the best performance .. especially on hills.

    Hope that clears up some questions. More out there by using SEARCH.
     
  6. May 17, 2011 at 2:49 PM
    #6
    supralight

    supralight [OP] Well-Known Member

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    To the 2 last replies: Everyone and their mothers knows what octane does, and what the manual says.

    But remember, pre-08 tacomas had the mentions of 91 octane offering better ''performances'' in their manuals. That leads to: maybe our ECU are programmed to advance timing for higher octane which LEADS to higher efficiency.

    That is the topic of this post, nothign else.

    Yesterday I switched from 87 octane to 94 octane, with tank nearly empty (approx 1.5 gallon left, needle passed empty line). I'll see if it still changes the trim, and if I get better efficiency.

    Please, people with a scangauge, try and experiment this!
     
  7. May 17, 2011 at 3:07 PM
    #7
    supralight

    supralight [OP] Well-Known Member

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    Did you have a scangauge when performing this? You won't notice a 3-4% fuel economy increase due to variables, nor a 3% increase in torque just by using your butt dyno.
     
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