STS N* v8 MPG
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Cadillac STS Forum - 2005 through 2012 Discussion, STS N* v8 MPG in Past Cadillac Vehicle Discussion; Hey I'm just curious what everyone else is getting. I have a 2005 with a v8 and I'm getting 11mpg ...
  1. #1
    Cadzilla8's Avatar
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    STS N* v8 MPG

    Hey I'm just curious what everyone else is getting. I have a 2005 with a v8 and I'm getting 11mpg average like 60/40 city/highway I know I shouldn't be expecting very high but still 11 is sorta embarassing haha. I also do not drive very aggressively like maybe once a week ill get it over 4000rpms otherwise nothing crazy.


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    curtc's Avatar
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    Re: STS N* v8 MPG

    I average about 20-21 with a 75/25 highway/city split...My car rarely moves outside of driving to work these days...If you are driving in a lot of stop and go traffic or encounter a lot of stop lights your mileage is being destroyed. The N* is a pig when not cruising down the freeway, pretty much a truck with 4 doors and a trunk at that point.

    How many miles on the car? When were the spark plugs last changed? Do you run fuel system cleaner (Chevron Techron) through your fuel system on a fairly regular basis (I do one bottle every 5k)?

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    sub613's Avatar
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    Re: STS N* v8 MPG

    Depends on your rear end Final ratio, I had a 2005 with a 2.73 and got 16 and 27.
    With the one I have now 2006, it has a 3.23 and 15 and 25.
    Runs great,with a clean Air filter, and Mobile 1.
    I used to have a HEAVY foot, but have calmed down a lot.
    Happy Motoring !

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    Cadzilla8's Avatar
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    I have a 2.73 ratio. Recently broke 40k miles on the odo. I have a big bottle of Lucas oil cleaner (etc) in the garage I will put some in next fill up. Not sure if the plugs were ever changed

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    carter's_sts is offline Cadillac Owners Connoisseur
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    That's worse than my V. Doesn't sound right. I get around 16, city/highway mix, with occasional hard driving.

    Quote Originally Posted by Cadzilla8 View Post
    Hey I'm just curious what everyone else is getting. I have a 2005 with a v8 and I'm getting 11mpg average like 60/40 city/highway I know I shouldn't be expecting very high but still 11 is sorta embarassing haha. I also do not drive very aggressively like maybe once a week ill get it over 4000rpms otherwise nothing crazy.

  8. #6
    Cadzilla8's Avatar
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    Yeah I wish I could get at least get into the 15 range. But with only 40k miles I can't think my plugs are shot... I changed oil and put new filter in before reset and I'm still getting 11.. I have a volant air intake too which shouldn't hurt my mileage

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    Awd v8s are worse than vs.

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    carter's_sts is offline Cadillac Owners Connoisseur
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    Re: STS N* v8 MPG

    That seems like a lot worse. Probably should be in the 15-16 range at least.

  11. #9
    EChas3's Avatar
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    Re: STS N* v8 MPG

    Zilla-

    If you've got a RWD N* w' 2.73, something does seem wrong. Crappy gas (ethanol) could contribute to your situation but 20 mpg hwy is NOT ambitious at all. Clean the throttle-body & change the air filter if it hasn't been done recently. I assume any idiot lights have received an appropriate response.

    To get the best mileage, keep the rpm's at 2k or under.

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    Cadzilla8's Avatar
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    I have brand new air filter in cleaned throttle body about 2 months ago and am relatively gentle on the throttle. Jason has lead me to believe it might be the fuel filter. I do have 40k miles and I am willing to be it's still the original 7 year old fuel filter on there.

  13. #11
    EChas3's Avatar
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    Re: STS N* v8 MPG

    40,000 miles isn't much on a fuel filter and if it's performing well, that doesn't seem likely. Later models don't even consider it a regular service item.

    But it's your car. It's in froint of the right rear wheel and takes a special tool.

    IMHO, Get your codes read by a good Cadillac dealer before spending any other money.

  14. #12
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    Since no one else said it, have you checked your intake manifold bolts?

  15. #13
    EChas3's Avatar
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    Re: STS N* v8 MPG

    ^^^ Very common and throws no codes.

  16. #14
    Guy.Seminerio is offline Cadillac Owners Connoisseur
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    Re: STS N* v8 MPG

    When I'm in NYC stop and go traffic ill get down to single digits mpg. On the interstate I do about 22mpg. Around here in Fayetteville it's a combination with some retardedly long lights and I really ring this baby out (love to hear the supercharger and feel it pull) and I average around 16mpg. When I used to drive in auto mode I used to get 15 but I noticed the transmission (which is different from yours) was reluctant to shift to 6th so I started driving in manual mode and improved mileage. The v runs the same ratio as the awd by the way, just more power and going to 2 less wheels. And more weight. You're low on mpgs. Not normal. Everything these guys are recommending sounds good. Check codes clean tb, all that.

  17. #15
    Cadzilla8's Avatar
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    Have no codes first thing I did check. I'm going to check manifold bolts though.

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