Poor gas mileage
 

Just got an 07 STS-4. Love the car but my gas mileage is not much better than my truck, and nowhere near the posting on the window sticker. Even at 55-60 with cruise on and no air, 23mpg is the best reading I can get, but who drives 55? I average about 18 coombined highway (70%) and city (30%). Anyone else notice this type of mileage? BTW- the AWD is supposed to only shave 1 mpg off the non AWD.

RE: Poor gas mileage
 

How many miles on that motor, it will get better as it breaks in, but honestly I get about 11 litres / 100 km or 23 mpg in my Deville on the highway and I thought that was excellent. I don't keep track of it in my truck, but with a 170 litre tank it seems like it goes forever.

RE: Poor gas mileage
 

all that Katz said plus on a car that size, tire pressure can make a big difference.
what type of fuel are you running?

RE: Poor gas mileage
 

Hey Gunzee

My 07 STS has 1100 miles on it. I just took a a 150 mile round trip and only averaged 23.0 mpg. I'm hoping that it's because it is still breaking in. Tire pressure set at 32 cold. Just me and the wife with 2 lightly packed suitcases. Average speed around 70 mph with air conditioning on. I thought it should have done a little better too. I have just rear wheel drive. My 01 Deville gets 27MPG on the same trip. However city driving on the DeVille was14mpg and the sts is giving me 16.0 to 16.5. I'll keep you informed as to my mpg progress. Going on another trip this weekend.

Eddiek

RE: Poor gas mileage
 

way too easy ..but .. are you guys setting the trans to overdrive?

RE: Poor gas mileage
 

Stomper

If we are supposed to be using a different a shift selection than "D" I'd like to know what it is. The selections are
P R N D. I would assume that D automaticaly uses over drive. It's a 5 speed automatic. There are no other selections that would indicate an overdrive setting.

Eddiek

RE: Poor gas mileage
 

Just took a 350 mile trip and still only 23 miles to the gallon. 1400 miles on the car now. I also had an added bonus. The hood popped open at 70mph on the trip home on the Ohio turnpike! The hood prior to that hadn't been opened for days to check the oil. I know it was closed because I did it myself. If I hadn't closed it properly it would have popped on the trip down and I would have had a warning message. Scared the s--t out of us. I'll inform my dealership ASAP. Maybe an adjustment?

Eddiek

RE: Poor gas mileage
 

Forgot to mention it only popped at the first notch. pulled over and closedit. Whew!!

Eddiek

RE: Poor gas mileage
 

99 sts n* always at 25 to 26 hgh trips...... with good conditions and running speed limit......????????? i think the sts did 27.? that was one time.... "the conditions"..wind at our backs, and mom was in the car......hehehe
all in all remember your driving a fat ride with a great American V8......how nice..... lets not complain........ whats a few bucks?$? dont ya love it?
rickyd

RE: Poor gas mileage
 

Rickyd

I'm only running a 3.6 v6 in my STS. Like I said before, my 2001 Deville N* got 27 mpg on the highway. Maybe it's still to new at 1400 miles.



Eddiek

RE: Poor gas mileage
 

ya i got a 89' fleetwood with a 4.5 and it gets like 11 or 12 in city and 18 on highway. Thats pretty bad but im pushin on about 260k miles.

RE: Poor gas mileage
 

1989 Fleetwood

You keep that machine runni'n man. With that many miles and theyearof that car, that's still pretty good. The point we were trying to make is that our vehicles are rated at 28 mpg highway. I hope we can can get that kind of mileage.
My 2001 Deville N* did. ( 260,000 miles, AWESOME!)

Eddiek

RE: Poor gas mileage
 

My 2005 STS V-6 gets around 22.5 average and around 25 on the highway. I live in northern KY where their is nothing but hills and gas milage is never what is posted. I have swithed my OIL to Mobil one Full Synthetc 2W20 whichincreased my gas millage from the original gas milage of 19 average and 22 highway. Take care and good luck.

RE: Poor gas mileage
 

Doug

Thanks for the info. Do you think it's ok to go to a 2w 20 weight oil? Owners manual and dealership told me
Mobil 1 5W 30. Any other problems other than your Bose 5.1 and paint chipping? I had to have the steering shaft replaced at 300 miles and the steering gear at 500 miles. New hood latch also installed yesterday. Steering shaft rattled like my 01 DeVille Steering Shaft.Steering gear made a banging sound when turning the steering to the left. Service dept. couldn't believe my bad luck.They always give me great service and fix my problems promptly.



Eddiek

RE: Poor gas mileage
 

You know I got terrible mileage with my 92 Bonneville 3.8 V6. Sometimes I think an N* V8 in a heavy car like a Cadillac will do better than a 6 just because in theory it has more power and torque and you are not leaning on it as much to get it going and keep up with traffic. No science here just my impressions from driving mostly V8's anda few V6's for 33 years.

RE: Poor gas mileage
 

Katzman's Caddy,

That thought had crossed my mind too. However, I have had several large GM cars with the 3800 engine including a 99 Park Avenue that gave me 28 mpg on the highway. My 02 Bonneville SLE did good too. Being that the 3.6 vvt is whole different design, maybe the gas milage is going to be a litlle less. I can usually get the hwy milage that shows on the sticker in the past. City driving has always been more of a challenge. Most of my driving is city and the 3.6 is doing better than my 01 N*. I guess I shouldn't complain. You are correct that N* sure doesn't have to work very hard.


Eddiek

RE: Poor gas mileage
 

eddiek, katzmans.....agree with you guys.....the n* not having to work as hard........though have been in Parks, and LeSabre that have got 30+ hgh......... same engine in a Bonniville and doesn't get but high 20's...... i think the Buicks are geared different, something with the tranny...... you Techs would know, thats imo.
rickyd