Occasional 89 Octane? Experiment coming this next week

Discussion in 'Gen 2 Prius Fuel Economy' started by silvergenII, Dec 17, 2015.

  1. silvergenII

    silvergenII Junior Member

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    My son the mechanic and I are in the middle of a discussion on octane and fuel economy so I'm polling the forum...

    Here in central NY there are No stations with so-called real gas available in 87 octane. He claims that with his 2012 Cruz, and with several of his prior vehicles he got more range out of 89 octane gas, filling up every other tank vs 87.
    Now that winter is here I'm noticing the usual slight decrease in range, about 30 miles per fill up. I haven't worried about the decrease, I know the causes a) the bladder is less flexible & b) the snow tires are on vs LRR etc...
    I've got a 500 mile trip (each way) coming up next week so I'm going to fill up with 89 octane that morning, & after work, see how far I can get before I need to fill up. He says I'll only make 400 miles as usual. I expect I'll make closer to 450. I wouldn't want to do 89 octane all the time, but I'm looking forward to seeing the results.
    This is a well known route, & I know about where I'll need to stop with typical traffic & what not. I typically run about 62-67 mph depending on traffic on the interstate. No hypermiling to help out much on this trip.

    Thanks for reading, I'll keep you posted.
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    E0 should yield 3% better gas mileage than E10. Remember to factor that out when trying to find the difference between 89 and 87 octane.
     
  3. silvergenII

    silvergenII Junior Member

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    So should 'expect' at best 12 to 15 miles more... Hmmm not even worth doing then.
     
  4. mmmodem

    mmmodem Taste Tester

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    Is E0 available at 89 octane. I thought it was only for premium 91 and up!

    Anyway, if your son has the 1.4 liter turbo Cruze then Edmunds has confirmed that premium gives better fuel economy than regular under some conditions. Save Money and Stop Buying Premium Gas

    The theory is that GM might have forced regular gas ratings by detuning a turbo engine that can use premium.

    I doubt the Prius will be the same but only one way to find out. Remember, even if you get more range, it has to be enough to offset the higher cost.
     
  5. wjtracy

    wjtracy Senior Member

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    The range will depend on energy content of the fuel (eg; density). E10 will reduce energy content 3%. But there is an unknown: the energy content of the base gasoline fuel. Without data. you don't know. But you could be up to 10% better with E0 - comparing an E10 fuel to an E0 fuel. You also could be worse with E0, so no guarantees here.

    One way to get data is try it measure range, but that's hard to see. Another way to get some simple data, what I would do, is I get exactly 1.5-gal in a Red gasoline can, and measure weight and convert to density grams/cc. This gives you some idea. Since density(energy content) is not a spec, it can vary. So there is no guarantee it will be same all the time.

    Generally the extra cost is not worth the extra range, but for those Prius owners trying to set the distance records (see threads) then these minor differences can be important.

    By the way, I am assuming from memory that Syracuse is not a Reformulated Gasoline region (that most Prius owners live in). There is essentially no chance to find E0 nor density difference in an RFG region. But your area yes, your son is possibly correct! And you actually do have some data, from your son, he says its better. That tells me there is some data.
     
  6. silvergenII

    silvergenII Junior Member

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    The only E0 available locally is 93 octane, which I Know my car shouldn't run on. Didn't notice the pump one day & filled up with it... At the time I was putting a tank a day in, so I used it up in a hurry.
    I doubt i will bother with trying it, I will simply drive with restraint & see how well it does.
     
  7. wjtracy

    wjtracy Senior Member

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    You can try the 93 but I am not saying its worth it,
     
  8. bisco

    bisco cookie crumbler

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    don't bother. you reduced winter mileage is mostly from the cold, longer warm up time and increased cabin heater. and yes, the snow tyres, plus the road conditions if there is weather, and more resistance from colder air. do you block your grille?
     
  9. silvergenII

    silvergenII Junior Member

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    The 93 won't be tried again... It was not happy that one tank full. Bisco this is my Second winter with this car. Funny thing is we are experiencing one of the warmest Decembers in recent history locally. Our temps on a daily basis have been in the 60s lately which for Central New York is incredible. My trip next week is from Syracuse to Northern Virginia. I figured I had a good opportunity to see how the car would run on 89 for those highway miles. I do not have the grill blocked yet but I am planning on doing it this weekend. If this weather keeps up i may just go pick up a set of summer tires and put them back on the car

    Here is my projected high and low temps for the next 10 days ImageUploadedByTapatalk1450375281.535246.jpg

    Syracuse has yet to have a measurable amount of snow this season the last time it was this late in the year was in 1898 and I'm running around on snow tires.
     
    #9 silvergenII, Dec 17, 2015
    Last edited: Dec 17, 2015
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  10. wjtracy

    wjtracy Senior Member

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    As far as we know, octane itself does not improve MPG.

    But one thing you can do is try to fill-up on conventional gasoline (not EPA Reformulated Gasoline RFG). We have RFG in North Va. and upthru Baltimore to DE NJ NYC area. The RFG is lower energy content to give cleaner burning potential. Somewhere around I-81 Hagerstown MD is the dividing line in MD between RFG and conventional.
     
  11. silvergenII

    silvergenII Junior Member

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    Wj I'm headed to the Shenandoah Valley next week and I won't be there long enough to get more than one tank when I'm there. I'm quite happy with my 44 something miles to the gallon even on E10. I was just curious what the result would be if I tried the tank or so of 89 octane.
     
  12. wjtracy

    wjtracy Senior Member

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    Shenandoah should be good energy content (non RFG) and cheap! You might even find some E0.
     
  13. silvergenII

    silvergenII Junior Member

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    Did some research, the only reason to increase octane is to reduce engine ping.
     
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  14. bisco

    bisco cookie crumbler

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  15. techntrek

    techntrek Member

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    93 should not have caused any problems. Technically it has less power available (you get more power from it in a performance engine for other reasons), but it should run the same as 87 in a Prius.

    I did a lot of testing with my '93 Caprice and found I got better mileage with 89 and 93, and after computing $ per mile, it was a wash no matter which octane I used.
     
  16. tvpierce

    tvpierce Senior Member

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    You forgot one:

    c) winter mix gasoline -- which should account for a 1-2% decrease in economy.
     
  17. techntrek

    techntrek Member

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    And:

    d) colder air which is much more dense, reducing mpg and range

    Ask any pilot how much more lift they get in the middle of winter vs. in the middle of summer.
     
  18. wjtracy

    wjtracy Senior Member

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    many reasons why cold is not our MPG's BFF LOL...not funny actually
     
  19. silvergenII

    silvergenII Junior Member

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    Had a good trip. I started with 70 miles on a casual fill up with E10 gas. i.e. not trying to top off , just fill until the pump stopped. That got me about 390 miles before I stopped for gas. On the way north I topped off with 6.5 gallons of E0, managed to get 480 miles, all the way from VA to Syracuse on one tank.
     
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  20. wjtracy

    wjtracy Senior Member

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    Wo there's some good Virginny moon shine...that's what I am talking about...E0 in a non-RFG region maybe has more energy content, for two reasons (1) no alky and (2) non-RFG base gaso.
     
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