Premium vs. Regular
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Northstar Engines and System Technical Discussion Discussion, Premium vs. Regular in Cadillac Engine Technical Discussion; I was told by the dealer that my 05 DeVille runs just fine on regular unleaded, but I look up ...
  1. #1
    RagingSamster's Avatar
    RagingSamster is offline Cadillac Owners Member
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    Premium vs. Regular

    I was told by the dealer that my 05 DeVille runs just fine on regular unleaded, but I look up the specs on the engine and the compression is 10:1 I thought the upper limit for 87 octane was 9.5:1 or else you risk problems from predetonation. Is this true, or has technology once again blew by me?

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  3. #2
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Premium vs. Regular

    Quote Originally Posted by RagingSamster
    has technology once again blew by me?
    yes


  4. #3
    Ranger's Avatar
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    Re: Premium vs. Regular

    Premium was "recommended" prior to 2000. After that compression was lower (just a tad) to allow for regular.

  5. #4
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    Re: Premium vs. Regular

    i have a 96, does this require 93 or can i use cheap stuff?

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    JimHare's Avatar
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    Re: Premium vs. Regular

    My 99 ran just fine for 100K miles on mid grade. Unless your 96 is sufficiently different, I think the recommendation was 89 octane.

    Even lower will not hurt the engine, the PCM will simply retard the timing a bit to forstall pre-ignition. You may simply give up a teensy bit of performance.

  7. #6
    fpmesiIII's Avatar
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    Re: Premium vs. Regular

    your 96 will run fine on 87

  8. #7
    peteski is offline Cadillac Owners Enthusiast
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    Re: Premium vs. Regular

    It will run on regular gas (slightly decreased performance) If you search this forum you'll find another thread which goes into how the engine deals with this. It is all based on knock sensors, variable ignition timing and the PCM. Northstar engine is "smart" enough to deal with this type of situation.

    Peteski

  9. #8
    Tommy Deville's Avatar
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    Re: Premium vs. Regular

    due to increased gas prices i alternate between super and regular, every other fill up or 2, I was running regular for a while after the 5th or 6th tank the car ran lousy, pinging and tapping, I went back to super and put half a gallon of lucas in, took it on the Highway and it was fine again.

  10. #9
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    Re: Premium vs. Regular

    I disagree with many replies in this thread, My 96 runs ok on 87, with a loss of power, but I get exactly 75-100 miles less per tank on that gas even 89 mid grade. With the 93 I can clear from 350 - 400 miles to a tank and a much smoother engine.

  11. #10
    Patrick7997's Avatar
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    Re: Premium vs. Regular

    Tactical64, I agree with you. My car runs like crap on 87. Serious loss of mileage and performance. 20% loss of mileage.

    And you know, back in 1999, Regular was around $1.40 here, and premium was $1.60, which was around 15% extra money for the premium. At today's prices, of $2.49 for regular, and $2.69 for premium, that's only about 8% extra price for the premium. Premium is a better deal than it's ever been....

    I'm getting more than 10% extra mileage alone, so, it's worth it money wise alone, to say nothing of the huge performance gain.

    And before I get flamed, I'm not just a premium freak. My Tahoe gets nothing but regular 87. I tried premium in that for a few tanks, there was utterly no difference in mileage or performance. None.

    In the ETC, there is a big difference. I do not know why, I just know I put premium in it now.....

  12. #11
    Ranger's Avatar
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    Re: Premium vs. Regular

    I ran 87 in my '97 Deville on the recommendation of our old guru. No change in performance (that I could tell), and no change in milage. Take it for what it's worth.

  13. #12
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    Re: Premium vs. Regular

    I don't know if my 95 Eldo is "special" but I got 430 miles on a tank of 87. And I live in the mountains in Tennessee.

  14. #13
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    Re: Premium vs. Regular

    Oh, and no pinging or strange noises.

  15. #14
    Zorb750 is offline Cadillac Owners Connoisseur
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    Re: Premium vs. Regular

    I get worse mileage on 87.

    2mpg every time.

  16. #15
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    Re: Premium vs. Regular

    My 96ESC runs fine with 87.

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