Regular vs Premium Gas
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Northstar Engines and System Technical Discussion Discussion, Regular vs Premium Gas in Cadillac Engine Technical Discussion; OK so as of today, Premium gas has hit $3.49 and up depending on where you buy it. I'm in ...
  1. #1
    Mitch3 is offline Cadillac Owners Fanatic
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    Regular vs Premium Gas

    OK so as of today, Premium gas has hit $3.49 and up depending on where you buy it. I'm in upstate NY and I know many of you are paying more. Off and on I have put regular fuel in my 94 Eldorado. It runs OK but honestly no where near as good as with Premium. Here's my question.......If I use regular on a steady basis do you think I will harm my engine? I can't believe that some stations are charging as much as 70 cents more for premium vs regular. My son-in-laws dad has a 96 STS and if he uses regular he gets a "Check Engine" message. I don't have any visible problems, it just doesn't have the pep etc. as it does with premium. My manual says I have to use premium. Going broke and need your advice. HELP PLEASE.........

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    EcSTSatic's Avatar
    EcSTSatic is offline Cadillac Owners Connoisseur
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    Re: Regular vs Premium Gas

    Search and you'll get a rehash of several threads on this!

    You have a knock sensor. It will retard your timing to prevent damage

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    Northstar will run just fine on regular. I have been using it for over three years. As mentioned, search the archives. I suspect a lot of the diehard premium only for my car guys will start changing their tune very shortly.

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    chance_b's Avatar
    chance_b is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    once i get my engine back in, i plan on only filling up with premium every 4 or 5 tanks, just to cleanse things out.

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    Mitch3 is offline Cadillac Owners Fanatic
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    Re: Regular vs Premium Gas

    Thanks. I appreciate the feedback. I have read a lot of the past archives but it still bothers me that Caddy emphasizes the fact that you MUST USE PREMIUM FUEL. My mother-in-law drives a big ass 1994 Buick with a big 8 and her manual says to use regular unleaded fuel. I think Cadillac is the only manufacturer that ever specified premium fuels since way back in the 60's. I tend to trust you guys more than GM so I will go with regular. BY THE WAY.........has anyone noticed that their mileage has dropped since this CRAZY GAS SHORTAGE !! started? I have always gotten 23 miles per gallon around town. All of a sudden my mileage has dropped to 20 mpg. Several other people in my office have checked and have found the same thing. Sounds like someone is playing games other than our government. We know they are playing games.

  7. #6
    jsjag is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    Quote Originally Posted by Mitch3
    OK so as of today, Premium gas has hit $3.49 and up depending on where you buy it. I'm in upstate NY and I know many of you are paying more. Off and on I have put regular fuel in my 94 Eldorado. It runs OK but honestly no where near as good as with Premium. Here's my question.......If I use regular on a steady basis do you think I will harm my engine? I can't believe that some stations are charging as much as 70 cents more for premium vs regular. My son-in-laws dad has a 96 STS and if he uses regular he gets a "Check Engine" message. I don't have any visible problems, it just doesn't have the pep etc. as it does with premium. My manual says I have to use premium. Going broke and need your advice. HELP PLEASE.........
    Well your question is always one that usually starts a fire. From what I have been told, as long as you don't get any pinging on regular unleaded, run with it. What I've been told the higher the compression ratio the higher the octane rating that will be given by the OEM. That doesn't mean that your car won't run on 87 octane nor does it mean you will ping.

    I've been told the higher octane will not produce as much (can't think of the term) but as much heat. So on a hot day 87 octane could give you ping but a higher octane won't ping.

    I belive that most octance grades have about the same amount of detergents. The mention of detergents......I think I read that modern gasolines don't have as much detergent as it once did.

  8. #7
    MWA
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    Re: Regular vs Premium Gas

    Figure the difference out per year. Why not put what the manufacturer recommends in it? Ranger, I thought you would recommend premium, because GM designates it that way. I have saved enough over the many years period that I owned Honda's, (1978-1993) if all of the fuel expense was prorated.

    Premium is still a mighty good buy.......for a Northstar. After who ever wants to drill where ever gets to drill what ever, it will come down. I never gave cheap oats to any horse that I owned either. Always followed Mr. Honda's manuals. Now that I own a premium automobile that suggest premium, I buy it. When I can't afford to buy it, I will purchase another automobile....but I have had the exquisite pleasure of driving the "best."

    Many thanks, Ranger!

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    Ranger's Avatar
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    Re: Regular vs Premium Gas

    jsjag
    From what I have been told, as long as you don't get any pinging on regular unleaded, run with it."

    The Northstar will not ping. It has a knock sensor that will detect spark knock long before you hear it and retard the timing appropriately.

    MWA
    "Ranger, I thought you would recommend premium, because GM designates it that way."

    I learned from the best. Actually, I think GM "recommends" premium for peak performance but says that you can use 87. Earlier model said it was "required". That was later changed to "recommended". I have been using 87 for over three years now on "Robs" recommendation and have noticed no effect on milage or performance. Now those to who would argue, I am sure if I had it on the track in a timed event there would be a difference, but the seat of the pants dyno can't tell. Try it, you may be surprised.

  10. #9
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    Re: Regular vs Premium Gas

    When I brought my 96ESC, the dealer I brought it from liked the car so much he started driving it himself. I asked him what type of gas he used and he said mid-grade. So I used mid-grade because I didn't notice any problems with the engine(not that I'm going to use whatever until I get a problem). I got to this forum and it says use premium so I stared using premium. Now in Chi-town the gas is $3.70 a gallon. Do you think I'm not going to go back to mid-grade or even low-grade. I feel kinda stupid for leaving mid-grade anyway.

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    MWA
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    Re: Regular vs Premium Gas

    Ok, Ranger and Al I will give it a try. Thanks for the posts on it. The difference per gallon is not that much yet, though, considering the big picture.

  12. #11
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: Regular vs Premium Gas

    Computer Controlled Ignition has a knock sensor and a program to adjust timing partially based on the knock sensor.

    There will be some differences in similar cars (tolerance stack), and in fuel from different stations on different days, but the only way to answer this question is to try the lower grade fuel in your car and see how it runs.

    Also see the effect on your gas mileage from different grades of fuel. You'll have to do some math but you may find you get better gas mileage with the premium and be able to justify the cost difference.



    I don't know in what size steps (degrees) Caddy pulls back the timing but that's part of the problem with giving a clear yes or no. To bad Bb ob isn't around. Maybe someone else knows. In the 90's it was usually 8deg steps.

  13. #12
    jsjag is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    I do not have a 1995 owners manual and I was wondering what is the stated the octane rating in the owners manual. On the dash it says premium only. "Premium" varies from State to State. In one State "premium" cound be an octane rating of 90 but in another State "premium" may be an octane rating of 92.

    Anybody with a 1995 Deville Concours N* manuall, please let me know the owners manual octane rating.

    Thanks

  14. #13
    Skotty is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    For as long as I can remember, premium has always been exactly 20 cents more than regular. I live in MO. Is this different in other states?

    Cadi is not the only line of cars to require/recommend premium. The Mustang Cobra I owned a few years ago also required premium gas. I always use premium when its required/recommended, given that it is only 20 cents more than regular. The day 20 cents a gallon decides whether I can drive my car or not is the day I know I am really in trouble. But if the difference is closer to a dollar in other areas, then the decision becomes harder.

  15. #14
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Regular vs Premium Gas

    Quote Originally Posted by EcSTSatic
    You have a knock sensor. It will retard your timing to prevent damage
    That's ASSuming it, the wiring, the connector, etc aren't damaged.

    Here's my recommendation, take it or leave it:

    If you can predict how you're going to drive for the next week, and you think you're never going to get above above 3000 rpm, get regular. You can save all sorts of money.

    IF - IF there is any chance you might need to go pedal-to-the-medal to merge onto highways, or race a honda next to you, do NOT chance it. Get premium. I absolutely hate relying on a knock sensor to retard timing. I really do. The best thing that could happen is you save $5 in gas for the week. The worst thing that could happen is you buy a new engine.

  16. #15
    ED's85GT is offline Cadillac Owners Member
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    Re: Regular vs Premium Gas

    Quote Originally Posted by jsjag
    I do not have a 1995 owners manual and I was wondering what is the stated the octane rating in the owners manual. On the dash it says premium only. "Premium" varies from State to State. In one State "premium" cound be an octane rating of 90 but in another State "premium" may be an octane rating of 92.

    Anybody with a 1995 Deville Concours N* manuall, please let me know the owners manual octane rating.

    Thanks
    My '95 Concours manual says:



    Fuel
    Use premium unleaded gasoline rated at 91 octane or higher. It should
    meet specifications ASTM D4814 in the United States and CGSB 3.5-92
    in Canada. These fuels should have the propper additives, so you should
    not have to add anything to the fuel.

    In the United States and Canada, it's easy to be sure you get the right
    kind of gasoline (unleaded). You'll see UNLEADED right on the pump.
    And only unleaded nozzles will fit into your vehicle's filler neck.

    Be sure the posted octane is at least 91. If the octane is less than 91, you
    may get a heavy knocking noise when you drive. (In an emergency, you
    may be able to use lower octane--as low as 87--if heavy knocking does
    not occur.) If you're using 91 or higher octane unleaded gas and you still
    get heavy knocking, your engine needs service.



    I have been using 89 octane in my 67,XXX mile "95 Concours with no
    noticeable adverse effects.

    Ed.

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