switching from 87 to 91 - Page 7
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Thread: switching from 87 to 91

  1. #61
    Platinum Member Silver2Coupe's Avatar
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    Quote Originally Posted by Swiftoy View Post
    OVERSIMPLE clarifications (rule of thumb)
    "premium" = self esteem felt with purchase of x.
    true value = miles (kilometers) per buck.
    -
    the denser the fuel (approx = average molecule size) the further you go per unit volume (gallon) = not greater than 0.5-1% per "octane" (compare consequent price increase)
    therefore lowest octane without knock = best value.
    alcohol = relatively lower density (but raises octane) "do the math"
    -
    combustion: best = predictable "slow" and complete burn allowing maximum useful energy to be extracted
    knock = explosion = high speed combustion due to burn caused by fast "(super?)sonic" high pressure wave front progressively igniting mixture.
    advertising marketing = extracting maximum bucks for minimum value! while making sucker feel good.LOL!

    Using the lowest octane without knock is the best value. Note I didn't say using something above 87 is wrong in a vehicle that states to use a minimum of 87 octane or higher.

    This is almost as bad as the great oil debate!
    There is still a lot of misunderstanding. Premium allows MBT timing which means its going to use the least amount of fuel and make the most power. I have run midgrade and premium in my car and seen the loss and gain of power and mpg. I have seen in my wifes car the loss of mpg and power but there is no driving style that worked to gain the mpg back. I never said the car would not run on regular but that is the lowest and it is more political than fact that they say run regular. There is a war going on and we are in the middle of it. Oil companies that can't make higher octane cheaply and car manufacturers engineers that are demanding higher octane.
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  3. #62
    One Bad Mama Jama!!! Swiftoy's Avatar
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    Quote Originally Posted by Silver2Coupe View Post
    There is still a lot of misunderstanding. Premium allows MBT timing which means its going to use the least amount of fuel and make the most power. I have run midgrade and premium in my car and seen the loss and gain of power and mpg. I have seen in my wifes car the loss of mpg and power but there is no driving style that worked to gain the mpg back. I never said the car would not run on regular but that is the lowest and it is more political than fact that they say run regular. There is a war going on and we are in the middle of it. Oil companies that can't make higher octane cheaply and car manufacturers engineers that are demanding higher octane.
    Agreed! I would still like to see higher octane fuel here in California we only see 91! I would like to see 93 like other states do but there is so much political BS involved.

    In an non performance car most people don't "need" higher octane fuel and the cost of using premium and gaining anything from it is not worth it for
    "most" individuals. I'm not saying there isn't anything to be gained but the car works fine on the minimum, so it comes down to is it worth the cost of the premium fuel. So for individuals who like to play the let see what kind of mileage I can get by doing this exercise, well then then the cost doesn't matter to that individual. Hell you can gain mileage "supposedly" by going to a high viscosity index oil such as TGMO which was designed with fuel mileage in mind.
    You can't fix stupid!

    Never argue with an idiot, they bring you down to their level and beat you with experience.

  4. #63
    Platinum Member Silver2Coupe's Avatar
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    Quote Originally Posted by Swiftoy View Post
    Agreed! I would still like to see higher octane fuel here in California we only see 91! I would like to see 93 like other states do but there is so much political BS involved.

    In an non performance car most people don't "need" higher octane fuel and the cost of using premium and gaining anything from it is not worth it for
    "most" individuals. I'm not saying there isn't anything to be gained but the car works fine on the minimum, so it comes down to is it worth the cost of the premium fuel. So for individuals who like to play the let see what kind of mileage I can get by doing this exercise, well then then the cost doesn't matter to that individual. Hell you can gain mileage "supposedly" by going to a high viscosity index oil such as TGMO which was designed with fuel mileage in mind.
    The Civic has a econ cam which can only be engaged when there is no knock and running MBT timing. Yes I agree oil will play a role but I only use Honda semi synthetic bulk oil and still get great mpg. I see a 10 percent gain in my van that requires regular only when I switched to premium but now that the cost is 45 cents more so it is not cost effective any more. My wifes car will use regular because she is use to the way it drives and its a safety issue for that decision.

    There is also a learning curve that goes with changing fuels and oils. The engine does get more efficient but it takes a few tanks just as with oil there is period the oil is cleaning and the additives start breaking down. Your driving style will have to change too and that is because if you drove the same way you will just use more fuel than needed so the benefit is lost. You can easy up on the pedal and have the same acceleration but using less fuel which is using lower loads at higher efficiency, using regular you wont see this and you usually have to give more fuel to keep accelerating the same.
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  6. #64
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    I filled up today with the first 1000 miles on this new car. Today's fill up is with with the 87 octane ethanol stuff. I'll check the mileage closely with the ethanol gasoline and see how it compares with the non ethanol 92 octane gas. So far the 92 octane gas delivered an average of 35 mpg with mixed driving, some mountainous and town, but no interstate high speed.

  7. #65
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    The 92 octane without ethanol runs perceptibly smoother and produces slightly more power in my car; but there is not much difference. Also, the 92 octane gets about 1.5 to 2 mpg better mileage. But is it worth it? Probably not; but it was an interesting experiment and now I know. I'll have more conclusive data with the next fill up.
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  8. #66
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    The only thing worse than ethanol gas are the politics behind it. If the 92 octane non-ethanol didn't cost $1.11 per gallon more than ethanol I would use it.

  9. #67
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    Quote Originally Posted by Spunjer View Post
    so i tried this little experiment ...... i was averaging 27 mpg, and 50-50 city/hwy.
    been using 87 ......... i did tried a tank of 89 to see if it helps with the mileage.........when i filled it up with 89, my mpg went up to 31mpg. i switched back to 87, and my mpg went down to 29. ..... i decided to go 91 from walmart (murphy gas). it went up to 34.5. ...... comments?
    I tried that too, switched from 87 to 89. Noticed NO DIFFERENCE! It's hard to believe that you can see a tank by tank difference for each type of gas.
    In reality fuel consumption depends on driving conditions, traffic,acceleration, temperature, load, wind velocity etc.
    I am useing a 20 mile roundtrip for my tests, same time of day, and cannot see any better miles with the higher octane gas.
    The Civic is optimized for use of 87 gas! Any improvement with 89 or 91 ia incidental.
    Save your money and use 87 regular.

  10. #68
    Truck? What truck?! scottyrocks's Avatar
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    You're know there is opposition on that claim, ds.

    At least one member has shown that the difference between 87 and 89 is minimal at best, but 91 or 93 does make a difference. You also need time for your ecu to adjust to the change to realize any significant change.

    And if you're gonna do the experiment, go big or go home. Iow, use 91 or better over at least 3 tanks, and then report back.
    Silver2Coupe likes this.
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  11. #69
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    Quote Originally Posted by Silver2Coupe View Post
    Yes premium gas is better. Try using top Tier BP which is what I use. I have not been using Econ for about 6 tanks now and my mpg is not as consistent but getting around 38-40 mpg 50/50 driving. In the winter I was getting 32/35 mpg but it was the coldest on record. Averaging 40 mpg with 50/50 driving with over 80 fillups. Last tank had a few cold days with snow and warm ups early last week and then just drove the car as hard as I could and got 37 mpg last tank with 50/50. I filled up today and getting 46 mpg just driving normal with no Econ. Econ is worth about 5 percent in mpg which is 2-3 mpg. The R18 will just run regular with out premium but when using premium gas there is a Ivtec with the econ cam that will get up to 25/30 percent better mpg. Using premium in a older car or lower compression motor its worth 5-10 percent in mpg alone but not worth the investment.

    The octane of the gas is going up and by late 2015 or early 16 regular will be 94 or 95 ron octane and premium around 100 ron. It wont be R/M method anymore and going back old school. No more mid grade.

    Also its good to reset the learned parameters by cleaning codes with out codes. It erases the fuel trims and the learned timing retard is set to default MBT timing and as long as there is no knock it will stay closer to that timing. Knock retard is a learned parameter and with regular it can take out 10 degrees or more which will also lower power and it adds more fuel which gets wasted in heat into the engine cooling system and out the tail pipe. 5 degree timing retard is about 1 percent in torque but after that it drops off faster so 10 degrees might be 5 percent or more torque loss across the board and not a efficient running motor. The more efficient the motor runs the less stressful the engine is when running (coolant,exhaust and even the trans).

    The best mpg in a tank I got twice. 48.9 mpg with 60/40 highway with econ on and with premium.

    Just noticed this when trying to troubleshoot a VERY heavy winter MPG drop (from around 32 (fall) to 25.6) lately and saw this about "...reset[ting] the learned parameters by cleaning codes with out codes."

    ① Should/could I do this on a '14 CVT sedan that I'm currently running and if so ② how do I go about doing it and ③ how can I check the amount of Ethanol I'm getting in my current blend from my local retailer?

    Thanks.

    Bill
    Ever since the advent of "smart phones", we aren't any smarter any more... we just know how to find it faster.

  12. #70
    Platinum Member Silver2Coupe's Avatar
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    You can reset the ecu but I would wait until you change the air filter. It takes about 5000 cycles for the ecu to adjust on it's own for ever load and rpm. All fuel sold will have up 10 percent ethanol unless otherwise marked. Ethanol is not the issue because as it warms it causes the engine to more efficient compared to pure gas. Your mpg will get better as it warms up outside and winter fuel is changed to summer fuel.
    Civic POP Crew #3

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