What gas do you put in your Prius Prime?

Discussion in 'Prime Main Forum (2017-Current)' started by charliebrownsprius, Dec 22, 2020.

  1. charliebrownsprius

    charliebrownsprius New Member

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    It's nearly time for us to fill the tank on our 2020 Prius Prime plugin in hybrid. In my neighbourhood, we have access to regular, mid-grade and premium gasoline.

    What grade of gasoline would you put in the car and why?
     
  2. Salamander_King

    Salamander_King Senior Member

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  3. MikeDee

    MikeDee Senior Member

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    Regular top tier, usually Arco.
     
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  4. eatriceyo

    eatriceyo Junior Member

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    regular 87 from costco
     
  5. huskers

    huskers Senior Member

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    Wait a minute. I have had my Prime for almost 4 years and now you are telling me it also uses gas???
     
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  6. PT Guy

    PT Guy Senior Member

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    Charlie, there is no benefit in any engine to using a higher Antiknock Index (AKI) gasoline that the engine maker specifies. 87 is spec'ed, and 87 works fine. There is no detriment to using higher AKI gasoline other than the cost. There are perpetual discussions about the wisdom or not of using gasoline without ethanol. Most of us use E10 (10% ethanol) 87 AKI gasoline with good results.

    Ethanol increases deterioration in old engines where the fuel system elastomers aren't adequate for ethanol. All modern engines are fine. Ethanol blended gasoline will hold more water in suspension, and in some small engines...lawnmowers, etc...in storage for months that can cause problems. Modern cars with sealed fuel systems don't have those problems. Ethanol has fewer BTUs per gallon, so there is a slight hit to gas consumption. Ethanol is the cheapest, least toxic way to increase the octane rating.

    Top Tier gasoline contains additives that exceed the minimum required by the regulators. It is wise to use it. Here's more: https://www.toptiergas.com/licensed-brands/
     
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  7. dbstoo

    dbstoo Active Member

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    I typically use Chevron Regular. Occasionally I'll use Shell or Costco instead.

    My typical driving pattern is to drive 3 to 20 miles a day, but once a month drive around 1000 miles. Depending on your driving pattern, it might be worthwhile to add Stabil gas stabilizer. :) I topped off my gas tank on the way home from one of those long trips last winter. I realized in October / November that I'd used NONE of it. I have since deliberately forced the car into hybrid mode to use up enough to add fresh gas. When I top it off this time I'll add Stabil, just like I do for my emergency generator.

    Dan
     
  8. The Big Sleaze

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    Arco near my house is normally mobbed, so about 1 in 4 tanks ends up being Chevron/Shell at 30% more (gasp) but feel I'm hedging my bets to get some Techron or whatever from truly top tier.
     
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  9. jerrymildred

    jerrymildred Senior Member

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    Hmm. It's been a while. Gotta think back to August. Just kidding. I always use 87. As said before, there's no benefit to using a higher octane than called for in the manual.
     
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  10. OptimalPrime

    OptimalPrime Member

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    I hate making a fool of myself, and if someone else wrote what I'm about to write, without my having had the same experience personally, I'd be skeptical at best.

    In my normal driving, whether local or highway, whether pre-COVID or now, I routinely use 87 octane. Pumps around here (New England) don't specify ethanol level, just the maximum allowable ethanol level "up to 10%". I'm pretty sure it's hit or miss as far as what percentage of ethanol is in 87 octane here, or any octane for that matter, though my impression that 89 octane is the most likely to contain much of it. The few times I've used 91 octane, no noticeable effect on mpg in New England driving.

    However, on long cross-country road trips, typically covering up to 1000 miles per day mostly at 84mph on cruise control, (or 74, 79, 89, or 94, depending upon what state I'm in) I have found that I get considerably better (say 8-10% better) mpg using 91 octane. It's not a placebo effect, as I was never expecting that, and certainly not hoping for it. All I can figure is that at higher throttle settings when fully warmed up, or perhaps when at higher altitude than I live at, the computer can get to some better timing/oxygen/lean-mixture points on the performance map that it can't get to without knock on 87 octane. Or that states out west simply don't put ethanol in premium gas, and I'm getting the higher energy density also. In any case, I'm a cheapskate driving near sea level at home, but you'll never catch me with less than 50% of the gas in my tank being 91 octane or higher when out west. I avoid 89 octane anywhere that doesn't specifically label it as the only E0 choice, figuring it's probably 87 with ethanol added.

    Maybe a little bit of it is psychological, not wanting to risk knock when turning off the cruise and doing more spirited big-mountain driving than I get to do at home. But in any case, I won't put 87 into an empty tank when driving the car hard, though I'll top up with it if stopping for food with a half tank of 91 in there, at a place where premium is unusually expensive.

    I realize this is anecdotal and hand-waving, but on vacation I don't feel like doing an engineering study to prove or disprove even my own anecdotes, despite being an engineer.
     
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  11. Storm88000

    Storm88000 Member

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    87 octane usually 6-7 times in row, then once in awhile I’ll fill with 93.

    Also, I’ve found my fuel efficiency
    improves perhaps 3-6MPG when filling with 93 octane. Whether or not that’s worth $2.58 a gallon vs $2.92 a gallon is debatable.
     
    #11 Storm88000, Dec 26, 2020
    Last edited by a moderator: Dec 26, 2020
  12. plug-one-in

    plug-one-in Junior Member

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    that is pretty good. I will try this 91 octane next time I pump gas.
     
  13. Hicksite

    Hicksite Member

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    What jerrymildred said.
     
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  14. Glenn G

    Glenn G Member

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    I have found that 3 of the Prii that I have owned had significant problems when getting going in cold temperatures (about 20 degrees F or lower). The car doesn't accelerate and it sounds like you're ruining the engine. The problem goes away when the engine heats up.

    This happens in my 18 prime and the 15v and also happened in my 15 II. I didn't have any issues of this sort that I can remember with my 11 II.

    Topping off the tank with "Hi Test" seems to solve the problem, so we run some premium fuel in the cars during the cold weather.
     
  15. ems2158

    ems2158 Active Member

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    On a recent drive up a long incline at around 20° F. I noticed what sounded like preignition knock when trying to accelerate. It stopped when I backed off the accelerator.

    I thought the knock sensor would prevent this. Maybe I got a tank of substandard gas?

    In this case I'll try some high octane fuel to see if this goes away.

    Anyone else experience this?
     
  16. PA Prius

    PA Prius Active Member

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    Gen1 PIP, so Prime-wanna-be here, but I'll respond since I didn't see that anyone else mention this. 87 octane and always ethanol-free if possible. Fortunately the closest gas station to us, less than half mile away, only sells ethanol-free.
     
  17. Gokhan

    Gokhan Active Member

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    The dealer fill was generic 87-octane. Currently I have Chevron with Techron® 87-octane. The next (third) fill could be Mobil Synergy Supreme+™ 91-octane. The octane ratings are 87, 89, and 91 here. The ethanol content, which is an mpg-robber, is apparently typically 10% here.
     
  18. SciRunner

    SciRunner Junior Member

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    Shell 87 or any top tier 87. I avoid non top-tier gas as previous cars always seem sluggish to move. I also avoid getting gas from New Jersey since some attendants continue to pump after the automatic fill closes.
     
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  19. Gokhan

    Gokhan Active Member

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    LOL Should I avoid New Jersey altogether? I've never been there. Is it any different than New York, which I've never been to either?

    Also, do you have attendants filling gas over there? I've never seen any in California or any other state I've been to.
     
  20. Salamander_King

    Salamander_King Senior Member

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    NJ does not allow self serve. You are at the mercy of the attendant to stop the pump at the auto-stop.
     
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