: Another Gas Mileage Thread



jimbohenson
03-04-09, 12:55 PM
I was wondering what kind of gas mileage people are getting. If you could please provide the following info that would be great. I am finding my mileage to be fairly horrible and am wondering if my expectations are too high. I have never owned a car with less than 8 cylinders and have never experienced 12mpg in the city except for my 05 CTS-V that sometimes returned only 9. I have owned a 94 STS, 96 Impala SS, 99 STS, 3 late 80's Caprices and have never gotten less than 15. I cant even hit 20 in my 05 STS V8 on the hwy with very conservative driving. I am gonna take it in to the dealer and would like a little bit of info to offer. It also seems that at hwy speeds the overdrive seems to get a little confused and the car is working to hard to maintain speed. Thanks in advance.



Year-2005
Mileage-44,000
Engine-V8
Driving Style-Spirited
Gas Mileage Observed City/Hwy-12/19-Not from DIC but with a Calculator between fillups and resetting the trip computer.
Percentage of City/Hwy- 80/20
Modifications-Corsa Axle Back
Fuel Grade Used-87 oct
Wheel and Tire Setup- 17x7.5 DTS wheels with 235/55/17 Vogues on all 4 corners.

mbnv992
03-04-09, 02:53 PM
I just bought my car new in august of last year, and the mileage is not the greatest. (I'm getting 16MPG mixed city/highway, but more highway than city).
Year- 2007 STS4 (AWD)
Mileage - almost 9,000 miles
Engine-V8
Driving Style- Easy on the "go" pedal 90% of the time.
Gas Mileage Observed City/Hwy- 16.4MPG hand calculated (NOT by the DIC)
Modifications- none, all stock
Fuel Grade Used- always 92 (premium)
Wheel and Tire Setup- stock 17" rims/tires

It will be interesting to see some more answers ! (Waiting to compare lol)

00deville00
03-09-09, 11:44 PM
one thing that may not help to much with the gas milage but would be better for the car overall is the fact that supercharged cars need a higher octane level than other cars so using 87 is probably not the best thing for it.

Guy366
05-28-09, 05:48 PM
I get between 17-18 MPG average on my 05 STS4 V8, about 75% highway driving. Doesn't really matter if I lay on the gas or not with all the highway miles. But I always use 93 octane. I would think those with RWD should be getting better gas milage - thoughts??

I should also mention I always use Shell V-Power BUT......... being in Milwaukee, I'm always running 10% ethanol, like it or not!

EChas3
05-28-09, 09:31 PM
2006 AWD V8 - 20 MPG @ 70 MPH (3.23 Gear)
2007 RWD V8 - 25 MPG @ 80 MPH (2.73 Gear)

87 Octane in both cases. Higher Octane provides only slightly better performance with little improvement in mileage.

HexWarrior5
05-28-09, 10:19 PM
My 05 STS V8 gets pretty good gas mileage...if you go to fueleconomy.gov, you can research the actual revised fuel mileage ratings for that specific year...on my car, i get about 18 - 20 mi/gal with about 60/40 highway/city driving. I just came back from a trip driving from the catskills to nyc (about 100 mi) and my car computer calculated 26.9 mi/gal for the trip!!! I've also done my own personal calculations with a calculator and fill-ups and the descrepency is about 5% if that...I think you should try and use the instantaneous mileage gage and just try and coast as much as you can.


P.S. I always use 93 octane and try to only fill up at shell or sunoco...dunno if that makes a difference, but that's what i do

jamesbalzer
05-29-09, 01:13 AM
I get about 17 in town and 22 on the highway. But, mine is a 1SG with the 3.42 ratio, V8, AWD. Not as good as I hoped, but certainly not bad considering the 320hp, full time AWD, 2400 RPM @ Hwy speed and 4200# car! Remember, though, that I live in Wyoming at 6200 Feet with wide open roads and light traffic.

Year: 2005 STS4 AWD 1SG
Mileage: 18,000
Engine: V8
Driving Style: Mixed, but generally never over 75mph
Gas Mileage: 17 City/22 Hwy
Modifications: None
Fuel Grade: Rotate 88/91 each tank
Wheels/Tires: Stock 18" with Stock Michelins

amgqmp1
05-29-09, 12:05 PM
* Year - 2005
* Mileage - 16,750
* Engine - V8
* Driving Style - Mixed: Spirited/Casual
* Gas Mileage Observed City/Hwy -15/27
* Percentage of City/Hwy- 95/5
* Fuel Grade Used - 89 w/ 10% ethanol
* Wheel and Tire Setup - Factory wheels, factory tires

If I use 91 octane (or higher) premium gas instead of 89, I get a 1.5-2mpg increase.

EChas3
05-29-09, 03:27 PM
* Year - 2005
* Mileage - 16,750
* Engine - V8
* Driving Style - Mixed: Spirited/Casual
* Gas Mileage Observed City/Hwy -15/27
* Percentage of City/Hwy- 95/5
* Fuel Grade Used - 89 w/ 10% ethanol
* Wheel and Tire Setup - Factory wheels, factory tires

If I use 91 octane (or higher) premium gas instead of 89, I get a 1.5-2mpg increase.

With that mileage gain (10%) mid-grade is a no-brainer. One gallon per tank saved for $1.70 or less. We see no difference in our (2006 & 2007) using 10% Ethanol diluted gas Reformulated for the Milwaukee market ($2.65/gal this morning!)

K STS
05-29-09, 11:01 PM
24mpg from Denton, TX to Cleveland, Oh. 2.73 gears.

KARL DAHLEN
05-30-09, 05:53 PM
08 3.6 DI V6. Now 29 MPG HWY (Hand Calculated, 400 miles, same route, same relative speeds (75 mph) after a K&N air filter and I now use Shell Top Tier regular with nitrogen. It really works! The K&N added 2MPG and the Shell another 1MPG. Mixed driving around 20MPG. Higher octane gas will do nothing except take more money out of your pocket unless your engine requires it.

hazcaddy
05-31-09, 07:40 PM
Just finished a mixed-use trip (hwy, city, and everything in-between) from Southern Ontario to Skyline Drive, Kitty Hawk, Virginia Beach, Baltimore inner city, countryside MD and PA, then back home by Interstate.

Total miles: 1819.
Average mph: 50
Overall fuel consumption (with an AWD V6): 23.7

I'm not displeased...

next2pool
06-01-09, 03:56 PM
08 3.6 DI V6. Now 29 MPG HWY (Hand Calculated, 400 miles, same route, same relative speeds (75 mph) after a K&N air filter and I now use Shell Top Tier regular with nitrogen. It really works! The K&N added 2MPG and the Shell another 1MPG. Mixed driving around 20MPG. Higher octane gas will do nothing except take more money out of your pocket unless your engine requires it.

For cars that don't specify premium, it is a waste. High octane gas is formulated to slow down the flame front in the combustion chamber--that's how it reduces pinging. The problem is that has the same effect as retarding timing--so in actual use it can reduce fuel economy and performance. Most cars today have knock sensors and can take advantage of premium fuel only if they have enough "authority" to keep increasing advance until it feels pinging. Many cars that don't require premium aren't programmed to allow enough advance to take advantage of it--hence reduced performance.

EChas3
06-10-09, 11:16 PM
2006 AWD V8 - 20 MPG @ 70 MPH (3.23 Gear)
2007 RWD V8 - 25 MPG @ 80 MPH (2.73 Gear)

87 Octane in both cases. Higher Octane provides only slightly better performance with little improvement in mileage.

This may have been a bit pessimistic in the AWD. I haven't had it that long and have not run a full tank on the Interstate. I did recently change the oil to Mobile 1 and the DIC claimed 22.4MPG after 30 minutes from a reset while cruising at 75MPH. It's still not great but could be a bit better than quoted above.

I think the dealer put in mineral-based oil when preparing it for sale. It likes the Mobile !! I think above 2,000 RPM is where the N* starts to suck gas faster. As I recall, the RWD 2.73 (17" wheels) was turning about 2,000 @ 80MPH. The AWD 3.23 (18" wheels) turns about 2,300 at 75MPH.

bigTYME
06-12-09, 12:32 PM
Year-2008
Mileage-28,000
Engine-V6
Driving Style-Spirited
Gas Mileage - trip computer average - 21.5mpg
Percentage of City/Hwy- 50/50
Modifications- none
Fuel Grade Used- 87 oct
Wheel and Tire Setup- stock 17s

porkfarm
06-15-09, 12:55 PM
I have 05 V8 and 07 V6 AWD both do better with TControl shut off. If it is not raining, I hit the TC button in the center console and mileage is up about 2MPG. 18 on the V8 22 on the V6. I am getting sick of the computer hitting the brakes for me !!!

STS28
06-16-09, 08:26 PM
Year-2005
Mileage-52,000
Engine-V8
Driving Style-normal
Gas Mileage - trip computer average - 20.2mpg
Percentage of City/Hwy- 70/30
Modifications- K&N intake, Flowmaster 50 Series Exhaust System
Fuel Grade Used- 92 oct
Wheel and Tire Setup- 20" kumho rims and tires

corvette00
06-19-09, 01:52 PM
I am driving a 2010 Camaro v8 this week and it is getting 2mpg better than my 07 N* awd

Force-1
06-20-09, 08:13 AM
Wife and I are off on a 4000 mile road trip in a few hours. We're taking the STS. A similar trip last year resulted in about 26.5 MPG overall. At least this year gas is quite a bit cheaper. :yup:

My C6 Corvette would get about 28 MPG on the same trip, but lack of trunk space keeps it in the garage. I would prefer to take it, but my wife's shopping excursions along the way prohibit it. :(

c5 rv
06-20-09, 10:19 AM
My C6 Corvette would get about 28 MPG on the same trip, but lack of trunk space keeps it in the garage. I would prefer to take it, but my wife's shopping excursions along the way prohibit it. :(

If you have a C6 coupe, you have more trunk space in the C6: 22 cubic ft. in the vette v. 14 in the STS. However, if you have a vert, it is less: 11 v. 14. I used to have a C5 coupe and could put all kinds of stuff back there.

Force-1
06-20-09, 10:53 PM
If you have a C6 coupe, you have more trunk space in the C6: 22 cubic ft. in the vette v. 14 in the STS. However, if you have a vert, it is less: 11 v. 14. I used to have a C5 coupe and could put all kinds of stuff back there.

I have a coupe; however, the back seat of the STS will require use too once my wife is done shopping! :bonkers:

c5 rv
06-20-09, 11:56 PM
My wife and I made a number of long distance trips in her Miata. Unfortunately, stores were more than happy to ship things home for her.

Thunder Gray STS
06-21-09, 05:21 PM
I have a 2008 STS 4.6, I recently went on a trip to New England from Memphis, and got 30.1 computer figured and 29.3 hand figured. I kept it between 65 and 75. I usually get around 21 in town 60% hwy 40% surface streets. I've had several STS's and this one truely amazes me with the mileage. I've never had one get over 25 on the hwy.

drb5392
06-22-09, 09:43 AM
Year-2008
Mileage-19,000
Engine-V8
Driving Style-Spirited (Trip driving I lock the cruise in at 75)
Gas Mileage Observed City/Hwy-17/26-Not from DIC but with a Calculator between fillups and resetting the trip computer.
Percentage of City/Hwy- 60/40
Modifications-None
Fuel Grade Used-89 oct
Wheel and Tire Setup- Stock wheels and tires.

desilpj
06-29-09, 02:04 PM
* Year - 2008
* Mileage - 21,100
* Engine - V8
* Driving Style - Mixed: Spirited/Casual
* Gas Mileage Observed City/Hwy -17/22
Percentage of City/Hwy- 70/30
l Grade Used - 87 w/ 10% ethanol
* Wheel and Tire Setup - Factory wheels, factory tires

I just returned from a RT to the midwest from the east coast. ~ 1,900 Mi. My gase mileage was between 28-29mpg.

Greg00coupe
07-01-09, 01:05 PM
'05 V8 RWD and I get 17 around town and 22 on the highway. Since some have mentioned I get 32-33 with a C5 with Corsa, headers and high flow cats. Amazing what 6th gear and aerodynamics can do.

nguyendot
07-12-09, 09:27 AM
I get about 12 in the city and 21-22 on the highway.

2006 V8 with 1SG 3.42. This thing EATS gas like I drink water.

Mobil 1 is what mine came with and what the dealer puts in.

Regulator
07-13-09, 11:41 AM
3.6 V-6 1SG package
I averaged 27.5 mpg on a 120 mile highway trip there and 25.5 back. 87 octane, on and off the gas for some of the trip. With steeper gears or going slower with the 3.42's, I could see hitting 30 mpg highway.

In the city, spirited driving, I am seeing 16-17mpg....which, in my opinion, is pretty bad.

EChas3
07-14-09, 10:08 PM
3.6 V-6 1SG package
I averaged 27.5 mpg on a 120 mile highway trip there and 25.5 back. 87 octane, on and off the gas for some of the trip. With steeper gears or going slower with the 3.42's, I could see hitting 30 mpg highway.

In the city, spirited driving, I am seeing 16-17mpg....which, in my opinion, is pretty bad.

I believe the top V-6 package is 1SC.

My wife's 1SE RWD can get 30mpg but who wants to drive 65? We'd rather get 25mpg @ 80. (87 Octane Shell from Pilot.)

Superjim
07-16-09, 08:55 AM
My wife's 1SE RWD can get 30mpg but who wants to drive 65?
We'd rather get 25mpg @ 80. (87 Octane Shell from Pilot.)


Now that statement I agree with.

Texas Jim

rook99
07-16-09, 09:16 PM
This may have been a bit pessimistic in the AWD. I haven't had it that long and have not run a full tank on the Interstate. I did recently change the oil to Mobile 1 and the DIC claimed 22.4MPG after 30 minutes from a reset while cruising at 75MPH. It's still not great but could be a bit better than quoted above.

I think the dealer put in mineral-based oil when preparing it for sale. It likes the Mobile !! I think above 2,000 RPM is where the N* starts to suck gas faster. As I recall, the RWD 2.73 (17" wheels) was turning about 2,000 @ 80MPH. The AWD 3.23 (18" wheels) turns about 2,300 at 75MPH.

If I put 18 on from 17 will my rpm's go up or down?

next2pool
07-16-09, 09:40 PM
It depends on the tire that's on the wheel. It's possible to have a smaller diameter 18" combination than a 17 combo.

306stang
08-21-09, 10:56 AM
i think i might have a problem. . .

i've been through three tanks
like to say spirited driving but more so taking it easy whenever possible.

05 v8
50k miles
stock rims
87 octane

i'm getting combined of 15 based on dic
based on my calculations from last fill up i got 14.5mpg

something doesn't seem right

even when i drove back from jacksonville, which was all highway, i averaged 15.5

any ideas?

C&C
08-21-09, 11:34 AM
i think i might have a problem. . .

i'm getting combined of 15 based on dic
based on my calculations from last fill up i got 14.5mpg

something doesn't seem right

even when i drove back from jacksonville, which was all highway, i averaged 15.5

any ideas?
When you did your 'highway test', did you reset your average mpg on the DIC? If you had logged alot of miles at 15, you'd need quite a few miles to get the average back to a representative value. Were your tires at recommended pressures? Were you running a reasonable speed? Were you running into the face or a hurricane? (okay, maybe that was a little bit smart-ass). Anyway, there are a lot of things to consider.

Do you ever set your DIC to instant mpg and see if your readings get into the mid to high twenties?

306stang
08-21-09, 12:02 PM
i would have been driving with the wind

i didn't reset the dic but you would think from a 5-6 hour drive the average would climb more than 1/2 mpg.

tire pressure??? . . . alright obama. that's ridiculous. it would affect it but not that much. it's not like they were low enough to wrinkle the sidewalls from a launch or anything.

going to make sure i reset this afternoon, gotta go for a short drive (about two hours, just over an hour on interstate then about 45min on backroads)

i'll give a more precise update when i get there.

EChas3
08-21-09, 01:29 PM
Is your temperature guage just below half-way? Trans in 'D'? (Sorry, but '4' or Sport Mode may make a difference).

I'd be surprised for tire pressures to make a big difference but 1-2 MPG is possible.

Have you tried a tank of Premium?

My AWD gets 20 Hwy (legal speeds only)

skozzy
08-21-09, 01:53 PM
I know this seems a bit out there but...my V8 Ford Exploder has some serious transmission issues and gets the same type of mileage. I did just replace the tires to new Goodyear Fortera Triple treads and the milage went up by about a mile per gallon better!
Not sure if this helps but something to think about.

K STS
08-21-09, 03:03 PM
Thats insane. I get 18mpg combined since I've owned my car, and I let it rip every single day. When I take highway trips, i get 20-22.

next2pool
08-21-09, 03:40 PM
[QUOTE=306stang;1978594]i would have been driving with the wind

i didn't reset the dic but you would think from a 5-6 hour drive the average would climb more than 1/2 mpg.

QUOTE]

You really should reset the dic, since a long history of lower mileage will take longer to overcome. Not all the manufacturers compute average miles per gallon in the computer the same way. My experience on the STS has been that recent mileage changes have very little effect on the average reading unless the dic has been recently reset.

next2pool
08-21-09, 03:45 PM
I know this seems a bit out there but...my V8 Ford Exploder has some serious transmission issues and gets the same type of mileage. I did just replace the tires to new Goodyear Fortera Triple treads and the milage went up by about a mile per gallon better!
Not sure if this helps but something to think about.

1 mpg difference between tire brands and construction is not unusual. Low rolling resistance tires for cars such as electrics or hybrids have a lot of trade-off's inorder to get that low resistance. Because ours are performance or touring tires they will have higher rolling resistance than some other sizes and applications. Individual tire constuctions are a closely held secret within each company and some are better than others in juggling the performance features.

306stang
08-21-09, 03:58 PM
yes temp gauge was just below half way and the trans was not in sport mode.

i'll clear it before the drive to see if it makes a difference

i remember in my truck, 05 f150 with 8" of lift on 37" tires my avg mpg would change like it was in real time (if that makes sense or is even correct). i had an Edge tuner in it and was great.

other than putting the car on the dyno and spinning the drums, what other ways are available to tune our cars? not looking for performance but to fine tune the engine.

ezstriper
09-27-09, 09:33 PM
across the board AWD creates a lot more drag and ads weight, in most vehicles that are RWD based going to AWD loses 3-5 MPG, every bit of drag cost you performance and economy, so unless you really feel you need it it's a huge waste of $$$$$

turnerbend
09-27-09, 11:27 PM
Year-2005
Mileage-52,000
Engine-V8
Driving Style-normal
Gas Mileage - trip computer average - 20.2mpg
Percentage of City/Hwy- 70/30
Modifications- K&N intake, Flowmaster 50 Series Exhaust System
Fuel Grade Used- 92 oct
Wheel and Tire Setup- 20" kumho rims and tires

What air pressure do you run in your 20's?