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  1. #1
    Veteran Member Four Rings
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    May 06 2014
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    20% e85 in the RS5

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    There were multiple discussions in the B8.5 S4 threads about running 20% e85 in states with 91, to boost octane safely.
    I did this and it worked wonders with a noticeable increase in power.

    Has anyone tried this on the RS5????

  2. #2
    Veteran Member Four Rings superswiss's Avatar
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    Nope, and the owner's manual is pretty specific about no more than 10% ethanol and other blends (Page 197). If my math is correct, 20% of E85 on top of the E10 we get here would push the ethanol to 27%. Car is not designed for that. Ethanol is corrosive and a poor lubricant, so fuel lines and pumps that are designed for E10 may not welcome this so much.


    '13 panther blk RS5, Ti pkg, blk leather/alcantara, nav pkg, sport exhaust, driver assist pkg, rear shade, alu kreuz, ECS spacers 15f/10r, ECS tru-float rotors, ECS brake lines, Hawk HPS pads, european delivery
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  3. #3
    Veteran Member Four Rings
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    Thank you - great info!!!!


    Quote Originally Posted by superswiss View Post
    Nope, and the owner's manual is pretty specific about no more than 10% ethanol and other blends (Page 197). If my math is correct, 20% of E85 on top of the E10 we get here would push the ethanol to 27%. Car is not designed for that. Ethanol is corrosive and a poor lubricant, so fuel lines and pumps that are designed for E10 may not welcome this so much.



  4. #4
    Senior Member Two Rings
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    Oct 26 2015
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    Norman/OK

    Quote Originally Posted by superswiss View Post
    Nope, and the owner's manual is pretty specific about no more than 10% ethanol and other blends (Page 197). If my math is correct, 20% of E85 on top of the E10 we get here would push the ethanol to 27%. Car is not designed for that. Ethanol is corrosive and a poor lubricant, so fuel lines and pumps that are designed for E10 may not welcome this so much.




    If the car accepts E10 then the fuel system system will be fine with any level of Ethanol in it. The reason for Audi not wanting to push more than E10 is the extra fuel needed to keep the air/fuel ratio at stoichiometric while under the part throttle map. When you go WOT the map switches over to the power enrichment tables which is a set table and again the ratio will be off slightly.

    I run up to 91 octane E20 in our 2016 Audi SQ5 with a EPL stage 2 kit on it, we dont get 93 octane where I live so we have to improvise some.

  5. #5
    Veteran Member Four Rings
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    May 06 2014
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    Napa, CA

    Gotcha - thanks.
    I'm too old to tune anymore, especially with the warranty issues that it will cause....
    Factory mapping and 91 for me, I guess.

  6. #6
    Senior Member Two Rings
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    Oct 26 2015
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    Norman/OK

    You can put pure 91 octane in the car and then add 2 gallons of E85, that will put you at 91 octane E10. It will help with detonation and will put you on part with what 93 octane gives you.

  7. #7
    Veteran Member Four Rings
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    Quote Originally Posted by TJay74 View Post
    You can put pure 91 octane in the car and then add 2 gallons of E85, that will put you at 91 octane E10. It will help with detonation and will put you on part with what 93 octane gives you.
    I love the suggestion, however, there's no pure 91 anywhere near me in Vegas that's less than 90 minutes away.
    Octane boosters are AWFUL - so what to do?
    It's almost a conspiracy - CARB in California essentially pushed West Coast refineries to produce 91 only in case gasoline might spill and cause a pollution problem.
    But that regulation was written so long ago, it essentially no longer applies.
    Gasoline spillage happens to infrequently it would be a zero impact and OCTANE has zero impact on vehicle emissions, regardless of what anyone says....

  8. #8
    Senior Member Two Rings
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    Oct 26 2015
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    Norman/OK

    You can still add the 2 gallons of E85 to the 91 E10 you get now. As long as you dont go over the E20 range you will be fine. I know that when I gas up at the half tank mark I need right at 10 gallons, I put in 1 gallon of E85 first then add the 91 in next. It helps with mixing the tank.

    The shop that installed my Procharger on my 2017 Camaro SS recommends using 93 E10 since it does better with knock suppression. You just have to improvise some in your case, and yes the knock additives are worthless unless you buy the really expensive ones.

  9. #9
    Forum Moderator Four Rings Loe's Avatar
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    Aug 09 2015
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    '14 Audi S5, '18 BMW 540i, '17 Jetta SE
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    many modern day cars can except a certain level of ethanol fuel (pretty much all of them, because of the mandated 10% here in the US, and the 25% in Brazil). The B8.5 fuel system wasn't designed for E85, but many of us run up to 50% (with fuel changes of course).

    On stock programming, you may not see any benefit though, in fact unless the fuel tables can adjust its trims appropriately, you may be doing more harm than good. If you have an ecu reflash to accept this, then you may be fine.
    -Loe P.-
    Audizine Forum Moderator

    ('14 Audi S5 S-tronic )
    [10.930@127.38mph | +1209 ft. D/A | 3.371 PR]



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