1990 Deville- premium gas question
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1990 Deville- premium gas question in Past Cadillac Vehicle Discussion; Do I still have to use the premium gas eventhough the Deville is 14 years old. The other day I ...
  1. #1
    annasr02 is offline Cadillac Owners Member
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    Question 1990 Deville- premium gas question

    Do I still have to use the premium gas eventhough the Deville is 14 years old. The other day I was driving and the car started to speed up on it's own, and the cruise wasn't on at all, I had to remove the key and pull over without hitting the person in front of me, eventhough I hit the brakes, it still wanted to go??? Crazy huh, well my son was in the back seat, so scary. I know that the gas doesn't have anything to do with it, but gas prices in California are very high, somebody please help!! Thanks

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    DeVillish's Avatar
    DeVillish is offline Cadillac Owners Connoisseur
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    Re: 1990 Deville- premium gas question

    yes you do have to use premium.

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    Giraffe }{unter's Avatar
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    Re: 1990 Deville- premium gas question

    Premium is the only way to go, Some gas station MORON put regular in my 1990 Deville after I told him 3 times to use super. The car ran a little rough and crappy.

    It's beyond me how somone can pump gas all day and night for years, and STILL not beable to get the RIGHT gas IN your tank, instead of spilling the WRONG gass all over your freshly waxed fender

    Today's gas prices are terrible, I can see why you want to switch to regular

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    CadillacQt's Avatar
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    Re: 1990 Deville- premium gas question

    Umm this is probally bad but I have a 91' Deville and I some times put regular gas in it cause its so damn expensive... I do put a fuel cleaner with every full tank so I think it may clean it.Does any one know if thats ok?

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    DeVillish's Avatar
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    Re: 1990 Deville- premium gas question

    its really not good for the car, i put 89 in mine once and i will NEVER do that again. It ran ruff and knocked a few times, not cool.

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    kevinK is offline Cadillac Owners Member
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    Re: 1990 Deville- premium gas question

    You may want to find out what is wrong with your car first.

    It could be a very dirty throttle body or rusty throttle cable. Clean it and see what happens.

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    CruiseOne is offline Cadillac Owners Member
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    Re: 1990 Deville- premium gas question

    HI - I only put premium in my '90 Brougham, otherwise it just doesn't run right.

  9. #8
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    Re: 1990 Deville- premium gas question

    Quote Originally Posted by kevinK
    You may want to find out what is wrong with your car first.

    It could be a very dirty throttle body or rusty throttle cable. Clean it and see what happens.
    start at the throttle body and also, always use premium

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    Emerald is offline Cadillac Owners Member
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    Re: 1990 Deville- premium gas question

    Quote Originally Posted by DeVillish
    its really not good for the car, i put 89 in mine once and i will NEVER do that again. It ran ruff and knocked a few times, not cool.
    I agree, I hope I never do it again. I did it by accident this past weekend. I am use to all the premium nozzles being on the far right side of the tripple pumps. Well I was out of state and at a 7-11 getting ready to head off to another state and thought well I'll fill up now. I was busy talking to the attendant and I filled it with regualr because I never looked. I just grabbed the hose on the far right. Thankfully it was only seven gallons and seemed to burn out pretty quick. I didn't like that knocking one bit..

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    Re: 1990 Deville- premium gas question

    I do know that it is not recommended! But you could use regular and
    rotate the distributor cap counter clockwise a couple of degrees to
    prevent knocking. I am not sure if using regular harms something
    else beside causing knocking. Well, if you retard the ignition timing,
    your car doesn't run as powerful as it should, so you tend to press
    the pedal more and as a result, you will get bad fuel economy.
    You will have to fill up more often, so overall, you may not save any
    money (and the car is less powerful).

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    Re: 1990 Deville- premium gas question

    Definately premium gas, regardless to how expensive it is. My gas pedal stuck, back when she was runnin. i almost hit the car in front of me too. Common cure, Jam the brakes on, it shocks the throttle cable. May want to get it checked out on a car thats that old.

  13. #12
    shredder130's Avatar
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    Re: 1990 Deville- premium gas question

    weird, i have ran 87 in mine for 2 years with no problems

  14. #13
    pink panther is offline Cadillac Owners Member
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    Re: 1990 Deville- premium gas question - explanation...

    Here is my understanding of why we have to burn premium gas.....

    The higher the octane - the slower the burn. Regular gas burns faster than premium.

    How does that work in your engine???

    When the piston is on the compression stroke, the spark actually ignites the fuel before the piston tops out. With premium gas, the resulting detonation is slow, or controlled, and the burning fuel creates a smooth downward power stroke of that piston (times eight - right?).

    If you are running the cheaper regular gas - the burnrate is faster - however, your cardoesn't compensate for that - so when the piston is coming up on the compression stroke, the spark plug ignites the fuel - remember, it is before top dead centre (TDC). Since the burn is fster - rather than a slow controlled burn, it is more of an explosion (BANG!!!) in the piston cylinder. Since the piston had not reached TDC when the fuel ignited - the piston is not "over the top" and the power explosion actually "knocks" the piston - trying to send it backwards against the momentum of the motor turning. That is why we hear "Knocking" when we run regular.
    The occasioanl use of regular in absolute emergencies, while not good for the motor, may - MAY not do harm, but no guarantees. Prolonged continuous use of regular, especially heavy footed driving, will definitely harm the motor.

    If you cannot afford the gas - why are you driving a full size car??

    My 94 DeVille gets me highway mileage comparable with my Volvo 240 wagon - I don't mind paying the extra premium premium to ride in style.........

    Hope my explanation helps...

  15. #14
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    Re: 1990 Deville- premium gas question

    i have never had a knocking problem

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    Re: 1990 Deville- premium gas question

    The best explanation of detonation and pre-ignition I have seen is on this web site:

    http://www.hastingsinc.com/Service%2...reignition.htm

    Courtesy of the Hastings piston ring company.

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