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Discussion Starter #1
I have read many threads about gas mileage.

I see that in most cases the V8 STS is getting 17 or so city and 22 or so highway.

I'm nearly all highway (55-65 mph) to work and back and averaging only 17.2.

I have read that it will get better...Dealer said it would get better...

I'm at 6400 miles now with no change from the first month I had it.

Turned in an '02 Seville, that over 3 year period averaged about 21.5.

Yah the new STS is more power,but 17.2 from 21.5 is like 20% drop. What am I doing wrong!!! What could cuase this drop? Is it California gasoline? BTW Has anyone figured out the combination/sequence for pulling up trouble codes...

Thanks in advance...
 

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Hard to say but if you are like most V8 owners you probably have your foot in it a little more that your 02. I also came out of an 02 SLS and have been in my 05 STS V8 since March. If I baby it I can definately improve the numbers but what fun is that. I never reset my running average and an about a 50 / 50 split city and highway and am running 17.6. I find it very difficult to move that number, I have taken some 200 - 300 mile highway cruises and my instant numbers are 22 - 23 but it takes a long time to move the average number.
 

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I drive 56 miles each way to work daily with only 5 of it being streets and see about the same as you (17ish).

This week I tried a "max mileage" and stayed at the speed limit, single lane and light footed ALL the time and had it up above 20 (20.2) for the first tank average. Added in a day of city drving and back to 19 at the moment.

I'm at 7200 miles and will wait until after the 10k roll to see where it goes. For a 5000lb sport sedan though I am not overly surprised.
 

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I also have about 17 mpg with my V8 even when I included recently about 60 miles of highway driving. I have reset the average mileage per gallon number on some of my fillups. I do not have a lead foot.
I have been told the car is still in the break-in period (I have less than 2200 miles). Based on the comments above, I don't think I am going to see much improvement. The 19 mpg city and 26 mpg highway numbers on the stickers are meaningless.
 

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EPA numbers are for a downhill run with a tail wind. As far as I am concerned anything in the 17 range around town ain't bad for a big V8. Highway is much better and you should see around 22 on a long trip. What sucks more is the tank size, I am filling up about every 250 miles. My 02 SLS would give me 300 miles on a tank.
 

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Discussion Starter #9
I have the two wheel drive version.
If I were just cruising around town and had only a short surface street communte I would be happy with 17, I just don’t like the fact that I get substancially less than 1) my 02 seville did and 2) than the highway EPA rating. Yes I didn't expect 27, but when I'm on a perfectly flat highway, with cruise set at 65, my instant mileage shows 21-23 tops, never close to the 26 rated. A/C off windowns closed, tire pressure good??? I honestly wonder if the overdrive isn't kicking in. I mention this because my first real problem with the car happened over the weekend, a transmission "jump" (shifted down while accelrating..at least that what it felt like) merging on freeway...that's the only way I can describe it now...makes me wonder?
 

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Could it be California emissions? I just got 30 mpg in my 05 STS V8 on the highway coming back to Houston from Roswell. Of course I was going down hill (Roswell is 3500 feet above sea-level, Houston is 50 feet above). I do reset my AVG MPG everytime I fill-up. I had the cruise control on the whole way set at 72-73 mph. In town I get around 14.2 mpg.
 

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Also keep in mind the EPA ratings are woefully outdated (1970's era) and are currently being updated/replaced. They are based on vehicle class catagory and are not vehicle specific. It's like assuming the Energy Star label on your new fridge or water heater is right on regarding the annual energy usage/cost. These are just large windows, not detailed ratings.
 

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I got about 12MPG city with my V8 1SG AWD. Considering the 17.5gal tank, I get about 200 miles per trip. This is very disappointing and strongly makes me reconsider my desire for the STS V.
 

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maxd123 said:
I got about 12MPG city with my V8 1SG AWD. Considering the 17.5gal tank, I get about 200 miles per trip. This is very disappointing and strongly makes me reconsider my desire for the STS V.
This is about what I am getting on mine, same configuration. I dislike having to fill up so often. Highway gets about 21, but both are way lower than the mileage stated on the sticker.
 

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Discussion Starter #15
At averaging 18.1 now...After 6 months. Still think this is low for all the highway miles I travel. But they did tell me it would improve and it has.
 

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"But they did tell me it would improve and it has." Yeh it improved all right, about 1 MPG. Since when does anyone at a car dealership speak the truth?
 

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Maybe you people don't care that you were "hoodwinked" but for Cadillac to publish such misleading figures (MPG numbers) constitutes fraud as far as I'm concerned. We're led to believe that if one is an "informed" buyer than you'll have a fighting chance. How can one have a chance if these "numbers" being submitted are UNTRUE? Isn't FALSE ADVERTISING a violation of our constitution?
 

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Well I can definetely agree that regardless, the range on the vehicle leaves something to be desired for any type of travel or daily commuting.

I know of a circumstance that happened last week with a 05' STS driver running the car out of fuel. DIC showed 14.7 gallons used "theoretically" leaving 2.7 total in the tank.

Of course not all of that is usable but 15.4% of total is a bit high to be unavailable.

No hills turns or hard driving. He was just commuting with the speed control active on a level highway at speed when the engine shut down. No sputters or couphs and unable to restart even to idle, a complete shutdown just like that...

He didn't even think it was fuel at first but had Caddy send out a tech with a can rather than the tow to check first.

Good news was that from the time he hit the OnStar button to the time the tech pulled up....8 minutes. And the tech called him back one minute after he hung up with OnStar to say he was on the way with an ETA.

The tech says he gets more "fuel" callouts on the STS than any other vehicle and only on the 05/06 models. Not knowing his credentials can only relate what I heard but the tech said the car has "saddle" tanks with a pump on only one side. He says the car doesn't transfer fuel effeciently between the tanks and so it is easy to use various total amounts depending on how the tank leveled and drew fuel. He also related (Which everyone knows) that the DIC info is very inacurate and that the analog gauge is the best measure while avoiding anything below an 1/8 like the plague.

Luckily the fuel pump didn't/doesn't trip like some vehicles and after putting in a single gallon it fired right up. Of course the gauges showed just below a 1/2 tank which is pretty good considering it was just above the line before. A gallon seems to really impress the STS sensor/gauges to read that much after being "dry"...

Oh well, live and learn but that means he is limited to just over a 200 mile range which is rather absurd considering it is a sedan and not a pony coupe.

I wonder what the range on the "V" will be. At least your "average time travelled" will help offset the amount of time you are sitting at the pump!
 

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ARTSBEST said:
Maybe you people don't care that you were "hoodwinked" but for Cadillac to publish such misleading figures (MPG numbers) constitutes fraud as far as I'm concerned. We're led to believe that if one is an "informed" buyer than you'll have a fighting chance. How can one have a chance if these "numbers" being submitted are UNTRUE? Isn't FALSE ADVERTISING a violation of our constitution?
Cadillac is just using numbers provided to them by EPA after testing on a model provided by Cadillac. I am sure that Cadillac provides them with a "representative" car in the class and EPA uses "real world" driving conditions.
 

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ARTSBEST said:
Maybe you people don't care that you were "hoodwinked" but for Cadillac to publish such misleading figures (MPG numbers) constitutes fraud as far as I'm concerned. We're led to believe that if one is an "informed" buyer than you'll have a fighting chance. How can one have a chance if these "numbers" being submitted are UNTRUE? Isn't FALSE ADVERTISING a violation of our constitution?
Direct quote from the EPA "Gas Mileage Estimates" Criteria:

The gas mileage estimates are based on results of tests required on new motor vehicles (cars and light
trucks). Designated pre-production prototypes of new models are driven by a trained driver on
a dynamometer, an instrument similar to a treadmill. The same tests are performed on each vehicle
tested, following approved procedures, as described in the Federal codes or regulations. These
procedures ensure that each vehicle is tested under identical conditions, therefore, the results can be
used with confidence to compare similar cars.
Two different tests and gas mileage estimates are done for each vehicle tested; a city estimate,
designed to represent typical everyday driving in a city, and a highway estimate, to represent driving
in a rural setting. The tests measure the waste substances emitted from consuming the fuel, not
the actual fuel consumed. From the measurement of emissions, EPA can estimate the miles per
gallon achieved by the
vehicle on average.
The test used to determine the city estimate
simulates a 7.5 mile, stop-and-go trip with an
average speed of 20 mph. The trip takes 23
minutes and has 18 stops. About 18 percent of the
time is spent idling, as in waiting at traffic lights
or in rush hour traffic.
The test to determine the highway estimate
represents a mixture of 'non-city' driving. Segments corresponding to different kinds of rural roads
and interstate highways are included. The
test simulates a 10 mile trip and averages 48 mph. ]Me test is rue when the engine is warmed up and
with very little idling time and no stops until the end of the test.
To make the numbers on the labels more useful for consumers, EPA adjusts the laboratory test results
to account for the difference between the controlled laboratory conditions and actual driving on the
road. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory
test results. Experience has proven that these adjustments make the nfflcage estimates on the labels
correspond more closely to the actual
gas mileage gotten by an average driver.

End Quote...
 
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