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Cadillac STS Forum - 2005 through 2012 Discussion, Gas mileage in Past Cadillac Vehicle Discussion; City driving is a killer. . . .I get like 230 per tank Highway is way better It's 4.6 BTW...
  1. #16
    samson_420 is offline Cadillac Owners Member
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    Re: Gas mileage

    City driving is a killer. . . .I get like 230 per tank

    Highway is way better


    It's 4.6 BTW

  2. #17
    EChas3's Avatar
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    Re: Gas mileage

    Cold weather & remote starts don't help much either.

  3. #18
    atlrus is offline Cadillac Owners Fanatic
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    Re: Gas mileage

    Quote Originally Posted by malatu View Post
    Ok, back on topic. Why would you think you could possibly get better gas mileage by going faster? It's always been my understanding that the faster you go the more energy (gasoline) consumed (as well as greater wind resistance).
    It's not a "think", it's a fact.

    As to why, CadiTamer's explanation makes perfect sense.

    P.S. Not only do I get better mileage at 90mph, it's also more fun to drive

  4. #19
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    Re: Gas mileage

    Yes, driving 75 mph in 5th gear is more efficient than driving 40 in 3rd gear but if someone thinks they are getting better gas mileage driving at 90 mph than at 65 mph they are greatly misinformed.

    This might offer some scientific explanation as to why you don't increase MPG by driving faster.

    http://auto.howstuffworks.com/fuel-e...uestion477.htm

  5. #20
    EChas3's Avatar
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    Re: Gas mileage

    It does depend upon the gear & torque converter lockup like Malatu observes, but drag increases geometrically with velocity through the air unless you are 'drafting'.

  6. #21
    atlrus is offline Cadillac Owners Fanatic
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    Re: Gas mileage

    Quote Originally Posted by malatu View Post
    Yes, driving 75 mph in 5th gear is more efficient than driving 40 in 3rd gear but if someone thinks they are getting better gas mileage driving at 90 mph than at 65 mph they are greatly misinformed.

    This might offer some scientific explanation as to why you don't increase MPG by driving faster.

    http://auto.howstuffworks.com/fuel-e...uestion477.htm
    Whatever guy, I don't know how to read simple numbers Of course you know better than me how much gas my car burns, why wouldn't you? After all, you know everything, right?

    Here is a quote from the article you apparently missed: " In general, smaller, lighter, more aerodynamic cars will get their best mileage at higher speeds. Bigger, heavier, less aerodynamic vehicles will get their best mileage at lower speeds.

    If you drive your car in the "sweet spot" you will get the best possible mileage for that car. If you go faster or slower, the mileage will get worse, but the closer you drive to the sweet spot the better mileage you will get. "

  7. #22
    malatu's Avatar
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    Re: Gas mileage

    I'm not suggesting your car or any other car doesn't have a "sweet spot". Though I am curious. What makes you think the sweet spot of your (our) STS is 90 mph?


    Quote Originally Posted by atlrus View Post
    Whatever guy, I don't know how to read simple numbers Of course you know better than me how much gas my car burns, why wouldn't you? After all, you know everything, right?

    Here is a quote from the article you apparently missed: " In general, smaller, lighter, more aerodynamic cars will get their best mileage at higher speeds. Bigger, heavier, less aerodynamic vehicles will get their best mileage at lower speeds.

    If you drive your car in the "sweet spot" you will get the best possible mileage for that car. If you go faster or slower, the mileage will get worse, but the closer you drive to the sweet spot the better mileage you will get. "

  8. #23
    Guy.Seminerio is online now Cadillac Owners Connoisseur
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    Re: Gas mileage

    The lower your rpms are the better off you're going to be. At 90 your car isn't exactly loafing along at 2k rpms. Also the faster you go the more of a negative impact drag has on fuel economy. My guess would be you get the best mileage when you're at the minimum speed your car will allow you to be while in the highest gear possible. For example in the v you can shift to 6th as early as 42-43 mph. This would be the sweet spot. Lowest possible rpms and lowest possible drag.

  9. #24
    EChas3's Avatar
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    Re: Gas mileage

    ...and lockup the torque converter to the extent possible....

  10. #25
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    Re: Gas mileage

    Agree: highest gear, locked torque converter and lowest speed will yield highest mpg.

  11. #26
    atlrus is offline Cadillac Owners Fanatic
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    Re: Gas mileage

    Quote Originally Posted by malatu View Post
    I'm not suggesting your car or any other car doesn't have a "sweet spot". Though I am curious. What makes you think the sweet spot of your (our) STS is 90 mph?
    I've already given my reasons earlier.

    I am not claiming that driving faster will increase your fuel economy. All I'm saying is that my STS gets the best mileage at 85-90mph.

  12. #27
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    Re: Gas mileage

    I think what some of the rest of us are saying is that what you claim goes against any 'standard', ever set forward, for mileage (ever published); maybe check those numbers again (I/we remain skeptical).

    And remember what George said to Jerry (on "Seinfeld"), "It's not a lie if you believe it". Still doesn't make it true though.

  13. #28
    malatu's Avatar
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    Re: Gas mileage

    Quote Originally Posted by atlrus View Post
    I've already given my reasons earlier.

    I am not claiming that driving faster will increase your fuel economy. All I'm saying is that my STS gets the best mileage at 85-90mph.
    Please share how you know your STS gets its best mileage at 85-90 mph.

  14. #29
    KRSTS is offline Cadillac Owners Enthusiast
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    Re: Gas mileage

    This defies the laws of physics

  15. #30
    atlrus is offline Cadillac Owners Fanatic
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    Re: Gas mileage

    Quote Originally Posted by KRSTS View Post
    This defies the laws of physics
    No, it does not. I love how everyone all of a sudden has a PhD in physics

    Ever thought that my STS maybe doesn't get as good mileage at 70mph as it should?!?
    There are many possible explanations as to why I get better mileage at 85 rather than 70. I never claimed that anyone else would, as well, although someone else earlier noted they've seen the same thing with their sts.

    I think what some of the rest of us are saying is that what you claim goes against any 'standard', ever set forward, for mileage (ever published); maybe check those numbers again (I/we remain skeptical).
    I couldn't honestly care less whether you are skeptical or not - It has zero effect on my gas bill I didn't post my experience here to seek validation, just to share it with the OP.

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