told not to use anything but regular gas..... true?

Discussion in 'Gen III 2010+ Prius Fuel Economy' started by k.s.c, Mar 25, 2012.

  1. k.s.c

    k.s.c Junior Member

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    My wife never forgets anything (especially when I screw up) and when we went to get some gas today I naturally went for premium since that was what I was used to in my previous car (this was the first time at the pump with the prius). My wife quickly yelled at me and informed me that during the orientation that I got when I bought the prius, I was informed not to put in premium and only use regular. I honestly don't remember hearing that but then again I was also too excited about the new car that a lot of what was being said went through one ear and out the other. I believe that they said I had to use gas with no more than 10% ethanol but I never heard premium being bad.

    Can anyone shed some light on this. We ended up leaving the gas station without filling up due to the fact we couldn't agree on things. Who is right here? Can I use premium or does it have to be regular?
     
  2. paycee

    paycee Junior Member

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    You can search from previous posts as this has been covered more than once but personally for me I'd go for a regular gas since its cheaper and prius engine is made to perform with a regular gas... but then again I have a gen II..
     
  3. Mocmylov

    Mocmylov Junior Member

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    Premium should be fine. The computer will adjust to the difference in octane. Just don't expect any better performance out of it or anything ;)
     
  4. k.s.c

    k.s.c Junior Member

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    so basically the car CAN use premium but in the sense of performance or longevity of the car, using premium does not "help" the car in any way and is basically paying a few dollars more and not getting anything more in return.

    So technically I was correct yet she was saving us money.
     
  5. krazypriuslady

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    my dealer told me regular gas only.
     
  6. Michgal007

    Michgal007 Senior Member

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    Use regular. Premium is a waste of money and some owners say it lowers the mpg.
     
  7. MJFrog

    MJFrog Active Member

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    Yes, you were correct...it shouldn't hurt. Yes, she was correct...dealer recommendation and saves $$$$.

    Apologize immediately!
     
  8. The Electric Me

    The Electric Me Go Speed Go!

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    I wouldn't sweat it.

    I remember Pre-Generation 3 release, it actually took a long time for Toyota to confirm what grade of gasoline the Gen 3 Prius did take.

    Regular is recommended and cheaper, so that is what I would use. But if you accidently put a tank of higher octane in? It wouldn't be the end of the world.

    Infact, just a ritual I have gone through for decades with my vehicle, whatever it might be, is every Oil Change, I run a tank of premium with a treatment of Techron included. Usually take a highway drive. I don't know if it really helps but my logic is it keep the fuel injection system cleaner.

    Usually these vehicles are designed with a minimum required octane, but if you exceed it, by accidently or conciously choosing premium it won't do any damage. You'll just be paying more for the tank.

    If you think about it, if running a tank of premium through a vehicle that's requirement is regular could do any damage? The amount of times this would happen would create a total mess for everyone.

    I live in Oregon which is a State that doesn't allow self serve. It's attendant based. And usually at least once a year the attendant will grab the wrong nozzle and fill with premium even though I requested regular.

    Except for the extra $3.00? It's a no harm, no foul situation.

    So in short, Your Wife was right...use regular. If you accidently fill with a tank of Premium? Uh...don't tell your wife, and you'll be okay.
     
  9. Mike500

    Mike500 Interessen-Gemeinschaft Prius

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    The myth about premum is that, because it costs more, it is better.

    Unless you need the "octane" rating for the particular vehicle to prevent "pinging," it is NOT better.

    Gasoline is composed of hydrocarbon chains of 6, 7, or 8 carbions linked together. Octane means the mix ratio contains more 8 chain carbion molicules. Higher octain means that it will not "pre-detonate" under higher pressures under higher compression ratios.

    It does nothing for lower compression engines.

    Under usual conditions, I do not purchase premium because;

    It is a lower seller, which means that it is less "fresh" than regular and has been in the underground tank longer to collect more water through condensation.

    To achieve higher octane, premium has a larger percentage of ethanol. If you look on the pump at the gas station, there is a sticker saying that it can contain up to 10% ethanol. Ethanol provides less mileage and collects condensation water more than gas without or with a lower precentage of ethanol in the mix.

    Ethanol must be used, since MTBE as an octane booster (methylbutyltertiaryether) was banned in 2005 in many states.

    So, regular is better functionally and financially in any model Prius.
     
  10. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    Bob Wilson (we all miss Bob Wilson) did a great deal of actual testing and graphing of ideas and not just accepting conventional wisdom. He found no MPG difference between octane grades but did find that full throttle acceleration up extended hills showed more power. Should you plan to cross the Rockies, that might be the time to buy Premium. But you won't see better mileage anytime.
     
    DaveC2007 likes this.
  11. Brett.

    Brett. Junior Member

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    Thee Prius engine is 13.0:1 that's hot roddin for a little 4 banger, haha.

    Doesn't need premium though, the engine hardly sees high enough RPM's to stay running let alone increased cylinder pressures. Detonation is virtually non-existent on vehicles without forced induction these days with modern fuel injection and cooling systems. Unless someone has been using crappy gas for 200K and the pistons are domed with carbon build up.

    Most vehicles these days are tuned for 87 octane fuel or thereabout and adding higher octane can lower gas mileage because of the 90+ octane fuels resistance to ignite. (As explained above me)
     
  12. dustoff003

    dustoff003 Blizzard Brigade #003

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    What does your owners manual say?


    Posted from my iPhone via the Tapatalk app.
     
  13. kevinwhite

    kevinwhite Member

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    Because of the Atkinson cycle the Prius uses, the effective compression is about 9.0:1 (about 1/3 of the mixture is blown out of the cylinder during the first part of the compression stroke.

    kevin
     
  14. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    The Prius has an Atkinson Cycle engine, the expansion ratio is 13 to 1, but the compression ratio is about 30% lower as the intake valves do not close until the piston is about 30% up the cylinder.

    Measuring from Bottom Dead Center to Top Dead Center does not yield accurate compression info in a Atkinson Cycle engine.
     
  15. kenoarto

    kenoarto Active Member

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    Using incorrect octane can do permanent and catastrophic damage to many cars. The owners' manual says to use regular gas. Consumer Reports has done a very good study on this. Why would you choose to take such a risk?
     
  16. Mike500

    Mike500 Interessen-Gemeinschaft Prius

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    Using higher octane gas does no damage to an engine requiring lower octane gas. Since highe roctane gas cost more, the only dmage that you're doing is to your wallet.
     
  17. V8Cobrakid

    V8Cobrakid Green Handyman

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    running higher gas can harm the vehicle.. it's not the engine.. it's the catalytic converters. now... those cost a pretty penny and i wouldn't want to be gumming one up with unburnt fuel just because i tossed in premium that the car simply spit out as unburnt exhaust. (of course this would take a lot.. and i mean a lot of premium fill ups to do)

    point being.. anything outside of what they ask, and you can technically cause more harm than you need to (i say More harm because running it technically wears it too)


    running anything over 10% ethanol can harm the vehicle (rubber gas lines and such)... if someone is running a generation II, it can melt the gas bladder.. which can spit up pieces and destroy the rest of the engine.
     
  18. Brett.

    Brett. Junior Member

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    Thank you for the engine info guys i gotta do some more research now, gives me something to do after work.
     
  19. Mike500

    Mike500 Interessen-Gemeinschaft Prius

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    What premium gas has over 10% ethanol?


    E85 should be run only in cars designed for E85.
     
  20. tach18k

    tach18k Member

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    On my 2012 II, I used regular 87 oct gas, got great milage, 47.5. I switched to mid grade 89 oct, my milage dropped to 44.2. I went back to 87 and i'm back at 47.5. go figure.....These figures are based on fillups and not Comps, also I saw my Comps drop too, about the same as I saw in milage.