Fuel - Regular /Mid-Grade or Premium?
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Cadillac STS Forum - 2005 through 2012 Discussion, Fuel - Regular /Mid-Grade or Premium? in Past Cadillac Vehicle Discussion; Dealer sez regular unleaded is fine for my 2005 STS... Anybody disagree or having good luck with 87 octane?...
  1. #1
    Space is offline Cadillac Owners Member
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    Fuel - Regular /Mid-Grade or Premium?

    Dealer sez regular unleaded is fine for my 2005 STS...

    Anybody disagree or having good luck with 87 octane?

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    STS2002's Avatar
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    Re: Fuel - Regular /Mid-Grade or Premium?

    Quote Originally Posted by Space
    Dealer sez regular unleaded is fine for my 2005 STS...

    Anybody disagree or having good luck with 87 octane?
    I have the V8 and it is recommened to use premium, however, i have used regualr and have not noticed a difference.

    Phil

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    don_mccarter is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    My V8 STS runs much smoother on premium.
    Premium is only 20 cents more than regular in my area.

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    ascariSTS is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    you can see it in the manual...


    V6 can have regular fuel... using premium on V6 is only a waste of money


    V8 must have premium only (high octane) ... don't try to use regular fuel... it will harm your engine

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    ewill3rd is offline Cadillac Technician
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    Re: Fuel - Regular /Mid-Grade or Premium?

    Whatever is says in the owner's manual.
    Using anything else is a waste of money and not really very good for your engine.
    Octane is a rating of "knock supression" used to identify the fuel you need based on the compression ratio of your engine.
    If you have a high compression engine you need a higher octane.
    Using high octane fuel in a low compression energy is almost harmful to the car.
    Just check the owner's manual and put in the octane level it calls for based on what engine is in the car.

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    BarryNS is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    This information is from the 2005 STS manual. You can see that using anthing 87 Octane or up is acceptable and won't harm your engine. Best performance is with 91 Octane. With the price of gas today it is understandable that many might want to use 87 most of the time.


    If your vehicle has the 4.6L V8 engine, use premium
    unleaded gasoline with a posted octane of 91 or higher
    for best performance. You may also use middle
    grade or regular unleaded gasoline rated at 87 octane
    or higher, but your vehicle’s acceleration may be slightly
    reduced. If the octane is less than 87, you may get a
    heavy knocking noise when you drive. If this occurs, use
    a gasoline rated at 87 octane or higher as soon as
    possible. Otherwise, you might damage your engine.

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    don_mccarter is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    Quote Originally Posted by BarryNS
    This information is from the 2005 STS manual. You can see that using anthing 87 Octane or up is acceptable and won't harm your engine. Best performance is with 91 Octane. With the price of gas today it is understandable that many might want to use 87 most of the time.
    I am sorry, but I for one don't understand paying 50+k for a car with
    a V8 engine and not spending 10 or 20 cents per gallon for better fuel.
    I have found that using premium fuel increases my MPG which makes
    the real cost difference even less.

  9. #8
    Cajonkev's Avatar
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    Re: Fuel - Regular /Mid-Grade or Premium?

    The local CBS News Radio station in LA did a walk-up poll (they approached people at the pump) and asked those buying premium why.
    The large majority was exactly what you just said. "If I can afford the car, I can afford the right gas to put in it. Why lower performance after investing so much." Of course out here with MTBE fuel, we need all the "umph" we can get...

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    ascariSTS is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    100% right


    plus, we are all want the best for our cars...

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    Skibanker is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    PLUS grade in the V6 gives me about 10% better mileage than Regular

  12. #11
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    Playdrv4me is offline Cadillac Owners 10000+ Posts
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    Re: Fuel - Regular /Mid-Grade or Premium?

    No point. My Northstar is a pre-2000 engine, which was before it was even assumed that you could throw regular in them without a problem, and Ive not noticed a lick of difference between regular and premium, not even MPG.

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    Re: Fuel - Regular /Mid-Grade or Premium?

    The duty of a knock sensor is to detect detonation. If timing has been retarded by the computer based on a signal from the knock sensor, it means detonation has already occured.

    Detonation is bad, mmmkay.

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    GEORGEC is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    Quote Originally Posted by ascariSTS
    you can see it in the manual...


    V6 can have regular fuel... using premium on V6 is only a waste of money


    V8 must have premium only (high octane) ... don't try to use regular fuel... it will harm your engine
    Please explain why you think it will harm the engine. The computer should retard the engine so that there is no preignition, thereby eliminating potential damage.

    George

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    Re: Fuel - Regular /Mid-Grade or Premium?

    The knock sensors have to detect detonation before they retard timing. By the time the computer responds, detonation has already occured. The idea behind knock sensors and computerized timing control is to allow you to drive your car in situations or places where high octane fuel isn't available. You aren't supposed to drive the V8 on regular all the time.

  16. #15
    psykiv is offline Cadillac Owners Fanatic
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    Re: Fuel - Regular /Mid-Grade or Premium?

    I put premium on the V6. The manual says that premium is recommended on the V6 (on the V8 its required), so that is what I will put.

    Also, I've noticed slightly better mileage with premium, so the price difference isn't much.

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