Curious what some of you V8ers are getting.
If you could give a brief report of what your getting and make sure you specify if you have a AWD if you do.

thx

Aceman

I have the 2002 STS, and I get approximately 24 to 27 on the highway

I have the STS, V8, rear wheel drive with about 2500 miles. In city could get only 16 to 16.5 and hwy about 18 to 18.5 until I changed the exhaust and partially redirected the air intake for more cold air. Just completed a 1000 mile trip after mods and now get 21.5+ on hwy with avg speed 76 and 19.5 to 20 in city. The car is/was starved for cold air and too much exhaust back pressure! More work needed. JES :helpless:

Spuron, I Have An 05 Sts V-8, And I Am Interested As To How You Installed A Cold Air Intake System/exhaust Back Pressure Improvement On Your Sts.
I Have Been Unable To Find A Cold Air Intake System For My Sts,
Any Information Will Be Appreciated. Robert

Spuron, I Have An 05 Sts V-8, And I Am Interested As To How You Installed A Cold Air Intake System/exhaust Back Pressure Improvement On Your Sts.
I Have Been Unable To Find A Cold Air Intake System For My Sts,
Any Information Will Be Appreciated. Robert
First I replaced the mufflers with best grade Flowmasters(about $90 each) and stainless steel 3.5" tips. So far have not changed stock cats, or increased stock pipe size. There is very little change in exhaust sound volume. Hardly noticable.

No one I have found to date like K/N makes an air filter yet. What I did do however was cut another 2 1/4" hole in the air intake box near the original 3 3/8" one. The cold air intake system is not much in the factory set up. Nothing more than a bad flappy rubber foam type material attempt to insulate it from the engine compartment. I did a bit of experiment behind the left 1/3 of the grill with existing rubber foam to attempt a ram cold air intake. The braces and headlamp washer mechanisms are all obstructions to a clean run for tubing or other sheet metal workings. However I do believe an aluminum or sheet metal design for the whole air intake housing area using 1/3 the existing grill can be used as ram, cold air intake for the area. Then buy an existing K/N filter larger than the existing filter, use the existing filter frame and replace with K/N filter material, securing it with black RTV material.

My success so far with the additional air to the filter box and the poor attempt of directing more air to the area leads me to believe this is the right track.

Also I placed a "Turbonator" (Google for it on the net, or make one after seeing it at an auto parts store) in the air intake tube after the filter. It helped in my 2002 STS.

The Al or sheet metal case (box) from 1/3 of the grill to get cold air to the air intake & fiter area is going to be a bear to fabricate I think. The grill and front end of the car removes quite easy to get at the work area, but---! However this should give a bit of ram air advantage at higher mph also.

Sorry to be so windy, but you asked and I'm desperate for better ideas! Suggestions anyone??!!

My 2 month old 05 STS V8 has 1789 miles on it. I have an average speed of 26 MPH and am averaging 16.5 MPG. I do mostly around town driving and since it's still new to me I can't seem to keep my foot out of it. I suppose if I toned it down a little I could probably imporve it by a few MPG. I have a 200 to 300 mile highway trip coming up and expect these numbers to improve.

I also have a V-8 with approx. 1625 miles on it. I am also getting about

16.4 MPG intown driving, without A/C. We will see this summer what the MPG will be.

2005 STS V8 with 3000 miles on it, RWD. 25+MPG highway at a steady 72-74 MPH. However, in city driving, although I really haven't checked carefully yet, I would guess it's only in the 16-17MPG range. I have been pleasantly surprised by the highway MPG.

2005 STS V8 with 3000 miles on it, RWD. 25+MPG highway.

1SE? or 1SF / 1SG?
RPM at that highway speed?

Thanks,
- Ray
Inquiring mind . .

Thanks Spuron, Your information was helpful and appreciated.
Robert

My 05 STS4 1-SG (9000 miles) with the 3.42 gear gets 15 mpg around town. Lots of traffic in Hotlanta and that's generally the type of driving I do... lots of stop-n-go, but the go is GREAT!

I took my first highway trip today in my 05 STS V8 RWD 1SE.
The round trip was 300 miles of 90 percent interstate. I filled
up before leaving and refilled at the same pump on return.
I set the cruise at 72-73 mph and used my foot to help out
when going around a few trucks, might have hit 85 once while
passing. Mileage was 24.7, I refilled until the pump refused to
pump anymore gas, so I think it is as full or fuller that when I started.
My overall city mileage has averaged 17.3.

Just returned from a 250 mile trip, NJ Turnpike from north NJ to Philadelphia. Rode hard down and back averaging around 80mph, got 22 mpg on an 05 STS with about 2200 miles on it.

2005 1sg with ACC and AWD. I got 21 mpg on the highway at 74-75 mph. I get 14-15 in town. A larger gas tank would be a real enhancement.

I have the V8 1SF and I am within my first 500 miles. I get about 14 mpg for 60% highway 40% city driving. I am being told that it is still breaking in and not to expect better numbers until later.
Is that true? :confused:

Yes, that is true. You will need about 4000 miles and then you should see a difference in the mileage. I have the 1SF model with about 6000 miles on it and burn only 87 octane. Just got back from North Carolina on Sunday. Was driving hard, about 80-85 mph. I got 22.4 with the 87 octane. Usually get about 16.6 in the city. I just do not think it is worth the extra money to go to a higher octane. Engine runs fine - smooth and no pinging. The car is fun to driveeeeeee on the xways.

Why would anyone buy a $50k plus car that requires premium fuel and burn regular to save $3 a tank. Gee, if it was designed to burn regular don't ya think GM would use that as a selling feature? You must be creating some negative effect on the motor that you will pay for in the future. Don't you want to optimize the car's performance? If you want good mileage and cheap fuel, buy a Toyota. I'll bet your Coupe DeVille ran on regular huh.

My all wheel drive V8 STS 4 is averaging an impressive 17.5 mpg. Not too bad....

V8 AWD w/radar gap gets me 23 mpg interstate - note the radar gap has a very "light foot" on the gas


Edwin M

Average about 15 MPG.
2004 SRX V8 AWD
14.8 - 16.8 All city driving MPG using 91 Octane.

Hope this isn't going to be a post bump. But, hey i've got a v8 sts4 and i fill up maybe twice a week and i get 16.1~16.2 mpg using premium.

I'm getting 16.7 in my V-8 with premium.

I'm getting 14mpg w/my sts4. But I got a lead foot.

Average about 16.4; just crossed 1000 miles.

I'm getting what I think is a terrible 17.7 mpg average. Drive the car to work on freeway and home, with traffic occassionally. My 02, which I turned in to get my 05 1SF, was getting 21.

BTW Bob in NY...my salesman told me it was OK to run car on regular 87 octane. I wasn't sure but 1500 miles on 91 and 1500 miles on 87...no appreciable difference in cruising or gas mileage- myabee a touch of a difference on accelertion but hardly notice. Manual says you may use 87 also. I'm going to see what servie folks say when I bring in for first service. I'm at 3600K, still using 87, not to save money, but because I think its a fraud.

Average 19 - 21 driving 75% suburban freeway. Average speed 35-40. All highway averages about 22 - 24. My 1SG has 13,000 miles on it. Every once in a while I'll put down a few feet of rubber and sometimes run up to 100 mph.

If I could keep my foot out of it, should get decent.. Mid 20's, but I have yet to leave the line under part to light accel. I do not know why, the car just begs me to drive it hard and fast...

Have really been pushing it lately. Love the handling. Made a sharpe right turn the other night at 55.. like it was on rails. Light tire noise, but vroom... Stuck it hard

I have a 2003 STS and I get about 22mph. I do about 70 highway and 30 city.

1SG V8 AWD with ACC has been getting a very poor 11-12 mpg around town. I averaged 20mpg on a long trip from NY to IN. I have racked up 4500 miles so far. Performance is great, but fuel economy is not. I didn't buy an STS to get great gas mileage, but I honestly thought I would get 14-15. It's gotta be the AWD that's dragging down the mpg.

I have accidentally filled up with regular two times instead of the BP/Amoco premium I usually use (daydreaming). I did notice a slight decrease in performance. I believe that all modern vehicles have a 'knock' sensor for lack of a better term that retards the timing when knocking is detected. Presumably in semi-expensive performance cars like the STS, this technology works quickly so the driver doesn't know anything is happening.

I have been told that the Northstar loosens up after 10K miles and fuel economy increases by 15-20%. I would welcome this increase as fuel in NY just hit $3.00/gallon for premium.