are you all sure I could use regular gas

Discussion in 'Gen 2 Prius Technical Discussion' started by little foot, Sep 8, 2008.

  1. little foot

    little foot New Member

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    it makes me nervous to use just 87 on my prius....
    I want it to last along time.
    Any thoughts...???
     
  2. KK6PD

    KK6PD _ . _ . / _ _ . _

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    What does your owners manual say????

    I'll bet it says 87 ONLY!!!

    Use 87, you'll be just fine!!!

    Pat KK6PD
     
  3. 9G-man

    9G-man Senior Member

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    What do you mean by "JUST 87."
    How do you perceive 87 octane is inferior, or would lead to damage, in comparison to a higher octane?
    Do you know what compression ratio is? And how it relates to the Atkinson cycle engine in your Prius?

    Don't fall for the misconception that a higher Octane gasoline is "more powerful" than a lower octane gasoline, it IS NOT.
    In fact, a lower octane gasoline ignites or explodes more easily, and has the same energy density. Which is just why 87 is what you need in a "low performance", low compression, Atkinson cycle engine, like the Prius has.
     
  4. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Four years and two weeks, 910 gallons of 87 octane gasoline, 49,000 miles.
     
  5. Dozzer

    Dozzer Prius Noob

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    BP sell petrol at an octane rating of 102 - It's double the costs of "normal" fuel!

    BP Ultimate UK - What is BP Ultimate 102?

    It's the same octane as Formula 1 cars use in hot weather.
    A Prius would probably blow up with it! lol

    I've seen it run on a Saab 93 turbo in a direct comparison on a dual rolling road at a motorsports show. "Most impressive..."
     
  6. 9G-man

    9G-man Senior Member

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    Octane ratings in the US tend to be 4-5 points lower than the same fuel elsewhere. That BP 102 would be 97 octane in the US. Formula 1 fuel is a high energy density fuel that is heavier than water, in a different leauge than gasoline, and it's characteristics are somewhat unrelated to Octane rating
     
  7. Dozzer

    Dozzer Prius Noob

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    Are you sure..

    Motor sport fuel regulation



    In order to comply with BS EN 228 all year round, this means that we have to increase the volatility of BP Ultimate 102 during winter months to meet a vapour pressure specification in the range 70 – 100 kPa. This is outside the range allowed in Formula 1, which only has a specification for summer quality fuel. Apart from this parameter in the winter, BP Ultimate 102 unleaded meets the current Formula 1 fuel specification. BP Ultimate 102 fully meets the current Formula 1 fuel specification in the summer months.

    F1 fuel is essentially the same as normal grade fuel but it's composition is strictly controlled.. BP102 is hand made in batches with a batch number. But you can buy it off the forecourt in some places in the UK.

    In most countries (including all of Europe and Australia) the "headline" octane rating, shown on the pump, is the RON, but in the United states, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, is 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and some even deliver 98 (RON) or 100 (RON).

    In the UK we use 95 RON octane (US - 90 to 91 octane).. Prius runs well.
     
  8. markderail

    markderail I do 45 mins @ 3200 PSI

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    Avoid the gas that has additives, like here in Canada, Petro Canada has in their gas a "cleaner", which is basically Ethanol.

    "Clean your motor while you drive"

    In reality, it's 10-15% less mileage, so you need to use / buy more gas, which you might end up over spending, because the higher price fuel actually contains more of their "additive".

    Stay away from that.
     
  9. David Beale

    David Beale Senior Member

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    Yes.

    Formula 1 fuel would not "blow up" the Prius. It would get poorer mileage on it as it wouldn't burn completely. You can buy aviation fuel of octane 115. It will also not "blow up" the Prius. It will give even poorer mileage in the Prius. For the same reason.

    There is no black magic here. The Prius system is designed to burn 87 octane rated fuel. Use that. Fuel that has "up to 15%" ethyl alcohol is also fine in the Prius (from the owners manual - RTFM!!!). Fuel with about 10% ethyl alcohol will give you about 3-5% poorer mileage, because ethyl alcohol has less energy in it. It will burn cleaner and will clean the engine.

    Now get the owners manual out of the glove box and take it inside the house and read it cover to cover. ;)
     
  10. qbee42

    qbee42 My other car is a boat

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    I was flying light planes back when the fuel industry stopped making 80 octane avgas. We had to switch over to 100 octane low lead. It didn't burn as well, and we had a lot of trouble with fouling. Coming in on a descent, you had to run the engine up periodically to clear the unburned fuel, or the darn thing would sputter and die when you needed throttle. Sputtering and dieing is never a fun thing when you need an engine in an airplane.

    David is correct: higher octane does not burn better, it's harder to ignite. If an engine is designed for higher octane fuel, it will use more compression to generate more power. If the engine isn't designed for it, you are just wasting your money for fuel that doesn't burn as well.

    Tom
     
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Also see Automotive Training and Resource Site which offers various Toyota tech training docs. Find Hybrid12 Engine Control System.pdf within the Technical Articles section.

    Page 2-8 of that file indicates that use of higher octane gasoline may result in starting problems.
     
  12. jdenenberg

    jdenenberg EE Professor

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    Tony,

    I just have to "one up" you. 2807 gallons, of 87 octane gas, 127,746 miles, 4 years and 5 months. Absolutely no engine problems in my 2004 Prius.

    JeffD
     
  13. jdenenberg

    jdenenberg EE Professor

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    Almost ALL gasoline in the US has 10% ethanol. It "only" lowers MPG by about 3% (not 10-15%) due to a lower energy density.

    JeffD
     
  14. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Daaaaaaaang. :eek:
     
  15. miscrms

    miscrms Plug Envious Member

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    Its interesting you say that. In general Saabs are one of the few vehicles where this actually is true (not 100% sure its still true). Historically Saab's turbo controllers have always run an adaptive program where they vary boost pressure in response to the quality of the fuel. The better the fuel you put in, the higher it will raise the turbo boost pressure and the better it will perform. The converse is also true, you can run low octane fuel and will dial the pressure back and not cause any problems. Pretty amazing that they implemented this system in 1982 using entirely analog components (no computer)! Because of its analog nature, people have also found it very tweakable :D Not that my '89 900 turbo convertible would know anything about that ;)

    Automatic Performance Control - Wikipedia, the free encyclopedia

    Rob
     
  16. miscrms

    miscrms Plug Envious Member

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    I'll second that. My '05 Owners Manual specifically says not to use higher octane fuel.

    Rob
     
  17. ekpolk

    ekpolk What could possibly...

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    This is not a concept that's alien to Toyota engineers either. The workhorse MZ series V-6 engines (still lingering on in the Highlander Hybrid in 3.3L form) performed the same trick. Here's a photo of the page from the manual for my 2003.5 V-6 Camry (with the 3.0L 1MZ-FE):
    [​IMG]
     
  18. ekpolk

    ekpolk What could possibly...

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    I hesitate to offer this next tidbit for fear of muddying the water, but I suspect that my 04 Prius was an outlier, or had some problem that had gone undiagnosed, and threw no codes. Mine would have occasional episodes of mild ping on acceleration. This would be quickly cured with a fill of mid-grade (in this area, usually that means 91 octane). Occasionally, I'd fill a half-full tank with 93 octane for a quicker cure. It always worked, and I never had a starting issue (but I never ran full tanks of straight premium either). And I still don't know why that car pinged.
     
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I've also noticed mild ping when climbing hills, on both my 2001 and 2004 using 87 octane Shell. I assume this is intentional - the ping demonstrates that spark timing is on the verge of being too advanced.
     
  20. qbee42

    qbee42 My other car is a boat

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    I agree with this assessment. The Prius runs its engine on the ragged edge of extreme efficiency. Any higher compression and it would be a mild diesel. It's amazing to me that Toyota manages to get this sort of efficiency out of a gasoline engine.

    Tom
     
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