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HT4100 4.1, 4.5, 4.9 Discussion, Premium Fuel in the 4.9? in Cadillac Engine Technical Discussion; Well put NODIH....
  1. #16
    cadillac_tech is offline Cadillac Owners Fanatic
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    Re: Premium Fuel in the 4.9?

    Well put NODIH.

  2. #17
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    Re: Premium Fuel in the 4.9?

    Always buy premium. In mountainous parts of the country, premium is already a lower octane to compensate for elevation. ALWAYS FILL WITH "PREMIUM"

  3. #18
    Head Hog is offline Cadillac Owners Member
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    Re: Premium Fuel in the 4.9?

    You guys are bigger risk takers than I am. I've got a 92 DeVille with a 4.9 with 89K on the clock. With gas prices as high as they are I've been tempted to try putting 89 octane in the tank, but given my car's age and how well it runs, I'd kick myself if I put some cheaper gas in it and wound up hurting my baby. My advice is to pay the couple extra bucks and stick with the premium.

  4. #19
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    Re: Premium Fuel in the 4.9?

    Cadillac seems to think it is fine with the appropriate timing change. I trust Cadillac personally.

    Is $4 a tank gonna kill you? Not likely, but for me driving 35K a year, yes, it adds up pretty fast.

  5. #20
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    Re: Premium Fuel in the 4.9?

    If you retard the timing you lose performance. If thats your approach to luxury cars, you should trade the Caddy in for a Corolla!

  6. #21
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    Re: Premium Fuel in the 4.9?

    If someone setup the timing at 6 degrees and 10 degrees, you would be hard pressed to even tell the difference. I experimented with both on mine running 87 and 93 octane. And honestly I could not find a reason what so ever to run 93 octane. Running around 8 degrees timing and 87 octane for 130K miles and 50K miles on 93 and on my log book, you never saw it in the mpg department, and I never once felt enough power improvement to even NEED 93 octane.

    If you drive quarter miles or race your Cad, then run 93, if you drive like a sane person, pocket the cash for other nice things for your ride. That for me is roughly $300/yr. I would rather take my lady out for a nice weekend than worry about tossing hard earned cash at the middle east for the "status" of running 93 octane all the time.

  7. #22
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    HUF
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    Re: Premium Fuel in the 4.9?

    Quote Originally Posted by N0DIH View Post
    If someone setup the timing at 6 degrees and 10 degrees, you would be hard pressed to even tell the difference. I experimented with both on mine running 87 and 93 octane. And honestly I could not find a reason what so ever to run 93 octane. Running around 8 degrees timing and 87 octane for 130K miles and 50K miles on 93 and on my log book, you never saw it in the mpg department, and I never once felt enough power improvement to even NEED 93 octane.

    If you drive quarter miles or race your Cad, then run 93, if you drive like a sane person, pocket the cash for other nice things for your ride. That for me is roughly $300/yr. I would rather take my lady out for a nice weekend than worry about tossing hard earned cash at the middle east for the "status" of running 93 octane all the time.
    Well put, NODITH. I have been running 89 at 8 degrees for some six years. Used to fill her up only with premium gas before. NO difference under regular conditions.

  8. #23
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    Re: Premium Fuel in the 4.9?

    I've tried to squeeze by putting in regular and I didn't get good results. The engine knocked and the acceleration was horrible, nothing like it is with premium. I don't even consider putting in anything other than premium now.

  9. #24
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    Re: Premium Fuel in the 4.9?

    Amoco 93 is the only thing that goes in my tank, I don't care what you guys say my car runs way better with that stuff than anything else.

  10. #25
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    Re: Premium Fuel in the 4.9?

    Quote Originally Posted by ZeroOctane View Post
    I've tried to squeeze by putting in regular and I didn't get good results. The engine knocked and the acceleration was horrible, nothing like it is with premium. I don't even consider putting in anything other than premium now.
    You did not set timing at 6 degrees right?

  11. #26
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    Re: Premium Fuel in the 4.9?

    Never ever run the 4.9L on regular withing changing the timing. Remember, by the time you HEAR the knock, it is VERY BAD KNOCK. So please do use the GM blessed timing values for the octane you are going to run.

    6 degrees = 87 octane
    10 degrees = 91 octane

    So you can likely safely extrapolate using 11-12 degrees with 93 octane or 8 degrees with 89.

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