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Cadillac STS Forum - 2005 through 2012 Discussion, Gas Mileage in Past Cadillac Vehicle Discussion; I don't like filling up so often but I'm not that worked up about mileage. I bought a fully loaded ...
  1. #16
    EChas3's Avatar
    EChas3 is online now Cadillac Owners Master
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    Re: Gas Mileage

    I don't like filling up so often but I'm not that worked up about mileage. I bought a fully loaded 3 year old STS at the end of 2008 for 1/3 of MSRP. When I was car-shopping most low mileage 3-year-old performance luxury cars (like my STS) were priced a lot more than $22,000 I paid (including CPO).

    Figure a worst-case-scenerio at $5 per gallon, 15 MPG & 10,000 miles a year. In three years, I would spend $10,000 on gas. On the other hand, lets say I bought a performance luxury car getting 25 MPG. I would spend only $6,000 on gas but I would have spent a lot more for the car; probably $30,000. My net loss would be $4,000. ($22k + $10k = $32k vs. $36k = $30k + $6k)

    If you figure the total cost of ownership, the STS is still a good deal. What's more, hybrids and electric cars aren't the good value that some would have you believe. (Even after the wasteful government subsidies.) Their break-even point is far past 100,000 miles even at much higher gas prices.

    Be happy! Gas is less than $4 per gallon and an STS gets a lot better than 15MPG.

  2. #17
    Midnight is offline Cadillac Owners Fanatic
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    Re: Gas Mileage

    Maiahsdad, what actual mileage are you getting? Your 215 miles per $60 could mean a lot of different things depending on gas prices and how empty your tank is when you fill up.

    I drive 64 miles a day (mostly 70-75mph highway) plus some sort trips and usually get a bit over 20. This is a 1SG V8.

  3. #18
    N0DIH's Avatar
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    Re: Gas Mileage

    I don't buy that at all.

    I have a 98 Lexus GS400, 300 hp @ 6000 rpm, 310 lb-ft torque @ 4000 rpm, 3.27 gears and I get 22-23 city highway, I can get 350-400 miles on a tank most all the time, and that is winter mpg. I was in the low 24's when it was warmer. I don't know highway mpg yet, haven't done enough to know.

    My 94 Fleetwood with LT1 and V4P package (7000# tow package) would get 19 in the same conditions, and only bested 22-23 mpg highway no matter how I drove. You are talking typical weight the car with me and junk around 5000 lbs.

    My mom had a 97 Deville "Y" Northstar (275 hp/3.11(3.15?) gears and would see 27 highway regularly.

    I would think the V8 STS should do more like my Lexus on a daily basis.

    Are you running 93 oct or 87? It will affect it some, my 00 Park Ave Ultra with a SC 3800 hates 87 octane and runs like crap on it (pulls too much timing out).

    Quote Originally Posted by chazglenn3 View Post
    It is the sum of those parts...AWD, V8 and 3.23 gear ratio equals a bad ass car that gets mediocre mileage. You bought a luxury performance car...not a Prius.

  4. #19
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    Quote Originally Posted by Midnight
    Maiahsdad, what actual mileage are you getting? Your 215 miles per $60 could mean a lot of different things depending on gas prices and how empty your tank is when you fill up.

    I drive 64 miles a day (mostly 70-75mph highway) plus some sort trips and usually get a bit over 20. This is a 1SG V8.
    That depends. I'm using the INST numbers to see how I'm driving. On the interstate driving 70-75mph, it will say between 10-15 for 10 miles or so. And if I accelerate ANY bit it'll drop down to 7 or so. Freaks me out. No gas smells at idle, nor rough idle at anytime. I've tried it filling with both 93 and 87. Same average number.

    I remote start for only the 10 minutes some mornings but not consistently. No codes either. My 99 STS was WAY better. And I drove THAT puppy HARD.

    Dealer found no issues.

  5. #20
    N0DIH's Avatar
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    Re: Gas Mileage

    Check the speedo accuracy. My GS4 is off by 2.5 mph, that translates into the speedo reading 2.5 LOWER than I am really going, so my mpg numbers were artificially low, a 1.05 correction on the miles made a difference.

    Check it with GPS or several high markers and a stopwatch, or like me, both....

  6. #21
    chazglenn3's Avatar
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    Re: Gas Mileage

    Going by the driver information center (which is not the most accurate way) my car is averaging 18.2 MPG. On the highway I usually see 22-24 on the display. But, I don't have AWD.

  7. #22
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    C&C
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    Re: Gas Mileage

    To the original poster; is your transmission shifting to top gear (is the torque converter locking up). At what rpm are you turning when you are running 70mph? Maybe a possible tranny problem, or, if torque converter is not locking up, the engine may not be going into closed loop operation (meaning the engine is running very rich). Time to think outside of the box (because your mileage is not normal).

  8. #23
    caddyfat2 is offline Cadillac Owners Fanatic
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    Re: Gas Mileage

    My 2005 STS4 1SG V8=14mpg city and 20 mpg hwy

  9. #24
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    Re: Gas Mileage

    I think the N* starts to suck gas above 2,000 RPM, regardless.

  10. #25
    GREGB1954 is offline Cadillac Owners Member
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    Re: Gas Mileage

    125 miles on 14.5 gal sounds like there is a problem. Our 06 N* with performance pkg gets 15-16 around town and 20-21 on the hwy. That is measured the old fashioned way: Dividing actual gal's used into total miles driven.

  11. #26
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    Quote Originally Posted by C&C
    To the original poster; is your transmission shifting to top gear (is the torque converter locking up). At what rpm are you turning when you are running 70mph? Maybe a possible tranny problem, or, if torque converter is not locking up, the engine may not be going into closed loop operation (meaning the engine is running very rich). Time to think outside of the box (because your mileage is not normal).
    I will shoot U guys (and gals if Ur represented here as well) a video and post on U tube. It'll show when it shifts and what the RPMs are at what speed. I will have the INST mileage toggled on as well. U guys tell me if it looks normal.

    Filled up yesterday. Drove about 40 miles and needle moved already. And I filled it up tight ($42 @ $3.16/gal of 87 this time).

    I ran 93 in my 99 STS religiously. But tested couple tanks of 87. Big difference in MPG, but still tons better than this car.

    Pretty sure I count 5 gear changes. And they change really quickly; like the ratio of a pro stock car (close together - not much drop in RPM between gears). Dealer dude says its the "performance-tranny) characteristic that I'm noticing. My 99 was somewhat like this, but I don't think this much.

  12. #27
    Midnight is offline Cadillac Owners Fanatic
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    Re: Gas Mileage

    Heh..."125 miles to 14.5 gallons" (what DDalder was getting)... something is definitely wrong or you're flooring it at all times. That's 8.6mpg. I think a spirited driven hummer H2 gets better than that in the city. You could probably propel the car by shooting a jet of gasoline out the back and get better than that, lol.

    The OP (maiahsdad)... it sounds like you're seeing around 12 average, which is also low unless you're doing some kind of extreme driving which it doesn't sound like it. My INST cruising along on flat highway at 65 is about 20 or so. So yeah the question is, are your revs high, is there some mechanical problem causing drag or wasting the engine's power (brakes stuck on, torque converter issues, some weird AWD problem maybe?), or is the engine just wasting gas, running rich...

    Another thing to maybe try, what's your 0-60 time, roughly, or in other words, does the car have all the power it should?

  13. #28
    ddalder's Avatar
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    Re: Gas Mileage

    For my dismal fuel economy, I do use premium (91 octane here). I always completely fill the tank and wait until I'm at 1/8 tank or less before doing so and therefore I'm confident my numbers are correct. I've never been one to drive my cars hard. Regardless, I'm going to watch my driving habits very closely over the next couple of tanks. If I don't see a large improvement, I'll check with my dealership to see what they can suggest. Even with winter, I didn't find these results last year. This winter has been much warmer and milder so if anything, I would have expected a gain. Just for comparison, I'm paying about $4.50/gallon (despite the fact we make the stuff here).

  14. #29
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    Re: Gas Mileage

    Hello everyone: as promised, I've uploaded a YouTube video HERE for you to check out. Tell me your thoughts.

  15. #30
    EChas3's Avatar
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    Re: Gas Mileage

    Seriously, watch your tach. It's easy to exceed 2,000 RPM in an AWD N* STS and mileage suffers greatly.

    On the other hand, if the cost of driving an STS bothers you that much, you're in the wrong car. There are plenty of high-mileage shitboxes available. Other luxury performace sedans will end up costing even more.

    ----------

    Quote Originally Posted by maiahsdad View Post
    Hello everyone: as promised, I've uploaded a YouTube video HERE for you to check out. Tell me your thoughts.
    Seems normal to me.

    The 3.23 gear revs higher and the tranmission control module programming holds it in gear rather than releasing in later RWD six-speed setups. Don't you like how the car slows when you lift your right foot?

    I can drive around town and not have to hit the brakes when the idiot in front of me slows for no reason. It's almost like driving a stick-car, i.e. the STS is a Sport Touring Sedan.

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