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Cadillac DTS Forum - 2006 through 2012 Discussion, Fantastic gas mileage on highway trip - 2008 DTS in Past Cadillac Vehicle Discussion; I get a consistent 26-27 mpg on the interstate ave.@70mph. Tires are @ 33PSI cold. My best to date was ...
  1. #31
    mgbumpus is offline Cadillac Owners Member
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    I get a consistent 26-27 mpg on the interstate ave.@70mph. Tires are @ 33PSI cold. My best to date was 29.1 MPG from Duluth, Mn. to Janesville, Wi. (360 mls @ 72mph Ave.) BP-93 100% gasoline. It was a very hot day - Over 100 Deg last July. Locally I lose 10% if I use E10. Who knows what I would get get if I played nice @ 55 mph or 65 mph.

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    I get a consistent 26-27 mpg on the interstate ave.@70mph. Tires are @ 33PSI cold. My best to date was 29.1 MPG from Duluth, Mn. to Janesville, Wi. (360 mls @ 72mph Ave.) BP-93 100% gasoline. It was a very hot day - Over 100 Deg last July. Locally I lose 10% if I use E10. Who knows what I would get get if I played nice @ 55 mph or 65 mph.
    rebel7254 likes this.

  2. #32
    kman779 is offline Cadillac Owners Member
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    Wish I could get 33mpg. The best I get is around 19 in town and 28 on the interstate doing 65-68mph which is better than quite a few of the others posting here. I havent given premoum gas a try yet so maybe I will try it and see if I can get even better mileage.

  3. #33
    tjwhite721's Avatar
    tjwhite721 is offline Cadillac Owners Fanatic
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    ALL,

    The NORTHSTAR engine is made to be driven HARD! The faster you drive the better the engine performs and the longer it lasts. You guys can drive 55 or 65 mph and have all that carbon build up in your engine if you want. I personally average between 80 and 90 (MPH) when I drive on the highway.

    There is no better feeling when you drive the DTS at 80+mph, with the windows down, feeling the smoothness of the car. The faster you drive the smoother it rides :-)

    I average 20mpg driving 80+ mph. I would rather drive fast and average 20mpg, than drive slow and hope to get 25+mpg.

  4. #34
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    .............

  5. #35
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Going 20 MPH over the speed limit isn't going to do much for keeping carbon buildup down. Do some reading in the Technical Archives.

  6. #36
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    Chuckj19 is offline Cadillac Owners Member
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    Quote Originally Posted by Submariner409 View Post
    Our fuel tanks have an air volume of about 1.5 gallons at the top of the tank to allow for fuel expansion and contraction with temperature - and that volume change is significant.

    That air volume is one of the factors that clicks off Pump A at so much fuel backflow and Pump B at another. The only way to totally fill a fuel tank (nowadays) to the max is to slowly trickle in that last 3/4 to 1 gallon of gas.

    The DIC indication of fuel used is very, very accurate, especially for quickie one-time fuel use looks. If you were to keep paper records over 5,000 miles or so you would then have a pretty good calculation of your average fuel consumption.

    I can fill the STS and spend a week in and around DC and wind up with an average 13 mpg - one "tank" of gas. I can then fill up and head down I-95 for SC and get 24.8 mpg on that tank............... but the average for the two tanks is 18.9 mpg. It takes a LOT of long term highway driving to pull that long term average DIC figure up into the 20's. I never reset my average fuel mileage figure - I do reset trip miles and fuel used readouts. Right now, mostly rural driving, the DIC says 19.3 mpg long term average.
    He never lied..

  7. #37
    rebel7254 is offline Cadillac Owners Member
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    I'm back.

    Believe it or not I actually forgot about this on the way down to the beach (it was a crazy morning and day), but I did remember to reset all fuel related DIC readings right after I filled up in Myrtle Beach. When I got home, I took pictures:





    As I anticipated, having the car loaded down with the extra passenger and luggage along with having to traverse the mountains brought down the MPG. But, I'm still quite pleased with 28.5 MPG all things considered. If you take the mileage and divide by the fuel usage manually, it actually works out to be slightly higher @ 28.8 MPG. Either way, as I said, I'm rather pleased and it's something I never expected with this car.

  8. #38
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    Your 2008 "DTS" - what is the 8th character of the VIN ?

    I don't think we ever determined if your car has a 3.71 or 3.11 final drive - and most of the Devilles (base, DHS) with the 3.11 see 27, 28, 29 mpg on the highway, long term, with ease.

    The acronym "DTS" for the new replacements to the Deville line is misleading because originally DTS meant the performance model, had the 3.71 final drive, and were lucky (like the STS) to get 25 mpg open highway.

    Glad the trip went well - We're headed from here to Myrtle Beach on 2 October - 4 day submarine crew reunion. For me, it's a 9 hour drive.

    Play with this for a while - but, as I posted before, using straight gas or E10 in either the car or trucks makes no difference in mileage for me -

    http://pure-gas.org/index.jsp?stateprov=MD

  9. #39
    rebel7254 is offline Cadillac Owners Member
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    Submariner, I never claimed to have the performance model. It definitely has the 3.11 final drive. The 8th VIN character is "Y".

    So with that in mind I guess my hope for becoming an instant millionaire is out the window?

  10. #40
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    No problem - ALL the VIN Y cars will beat a VIN 9 car in the gas mileage department.......... but the original 300hp/3.71 DTS association dies hard.

    There was a mileage thread in Seville a few years ago, with spreadsheet figures - for an ESC on a long trip .......... that one got just about 30 mpg, including mountains, with 2 people and some luggage.

  11. #41
    Superjim's Avatar
    Superjim is offline Cadillac Owners Connoisseur
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    I took a 500 mile trip over the past weekend...
    VIN 9
    Got about 20mpg...

  12. #42
    big greg is offline Cadillac Owners Fanatic
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    Quote Originally Posted by Submariner409 View Post
    No problem - ALL the VIN Y cars will beat a VIN 9 car in the gas mileage department.......... but the original 300hp/3.71 DTS association dies hard.

    There was a mileage thread in Seville a few years ago, with spreadsheet figures - for an ESC on a long trip .......... that one got just about 30 mpg, including mountains, with 2 people and some luggage.
    My 01 seville would always see 31-33 mpg cruising 65 mph. I loved it. Still gets about 29ish. 130k that car still rides and runs awesome

  13. #43
    jazoo is offline Cadillac Owners Fanatic
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    Re: Fantastic gas mileage on highway trip - 2008 DTS

    Quote Originally Posted by rebel7254 View Post
    Believe it or not I actually forgot about this on the way down to the beach (it was a crazy morning and day), but I did ........ home, I took pictures. ................As I anticipated, having the car loaded down with the extra passenger and luggage along with having to traverse the mountains brought down the MPG. But, I'm still quite pleased with 28.5 MPG all things considered. ...... slightly higher @ 28.8 MPG. Either way, as I said, I'm rather pleased and it's something I never expected with this car.
    rebel7254, Congratulations, that you were consistently getting ~28.5 MPG with your style of driving and where & how you were filling up the tank. We are never going to come to a solid conclusion on this issue as there are too many variables associated with this subject matter.

    Anyway, I applaud your persistency.

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