: '05 V stock tune: a little fat from the factory?

05-04-06, 11:50 PM
My weekly toll of $52 fillups is starting to make me wonder: how many miles should I expect per tank for 70% city / 30% highway driving? So far I haven't broken anything better than 16.8 MPG (average) with a range of 280mi. per tank. Since the Magnaflow was added, I've also noticed a fine layer of dark soot on the rear of the car... the white background and raised letters of the license plate help to highlight this.

I should get off my ass and log a few runs with autotap to monitor injector duty cycle, MAF readings, primary O2 sensor values and LTrims, but I haven't pulled the laptop out yet.

If StealthV is listening, can you confirm my findings or do you suggest a PCM reset first? Have you noticed an improvement in fuel mileage after the mail-order tune?

Seattle CTS-V
05-05-06, 12:47 AM
16.8mpg is considered pretty good on this board. I get btwn 12 and 13mpg average.

NH Vrod
05-05-06, 10:12 AM
Im getting between 19 & 21, with out a magnacharger, but am just about ready to order one. Is this what I can expect to see for gas mpg after install?

05-05-06, 10:23 AM
My drive is about 95% city and If I drive like a granny I see 16.8 on the car's computer mileage.

05-05-06, 12:28 PM
I drive like an old man most of the time ('cause I am one) and mostly city/some highway driving I get high 15-16 mpg. No maggie, just Corsa, UUC and FFCAI (K&N filter). EPA ratings for this car are overstated, as they are for all cars, but it appears your mpg's are in line with what you might expect. Keep in mind you have a high-performance V8 motor and given that, your mpg is really quite good compared to what others drivers are experiencing with substantially lesser cars.

05-05-06, 12:38 PM
If I do alot of city driving depending on how I drive it, I get at max 16...but for the most part im 50/50 so I average 18.6 I think, and thats only doing 65-75 on the highway getting about 24-26 mpg.

05-05-06, 01:13 PM
13.9 here

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05-05-06, 02:43 PM
Under normal driving, the factory PCM will always shoot for a 14.7:1 AFR based on feedback from the front O2 sensors. This is true regardless if one added an exhaust, headers, CAI, etc.

At WOT from the factory, the AFR is on the rich, conservative side. All other times it will be at stoich.

Imperator, your 16.8 mpg with a 70/30 drive cycle split sounds normal to me. If you're crusing around town in 4th gear at 30+ mph, try 5th or even 6th (35+) to increase your mpg. If your fuel economy has recently decreased along with more carbon on the rear, it may be due to the human side of wanting to hear your exhaust system emit its song and using more of that rich WOT mixture.

If one were to go for max fuel economy via an "aftermarket" means, +4 mpg is possible with the caveat of increased emissions, possible EPA non-compliance and a voided warranty.

05-05-06, 03:10 PM
Thanks for the confirmation... I've owned (and tuned) a modded LS1 F-body and C5, and just thought my mileage in this CTS-V is worse than expected. I suppose my figures are right on target though. I'm familiar with lean-cruise but haven't experimented with it much and assume it might damage the catalytic converters.

05-05-06, 03:24 PM
The mileage is incredibly bad if compared to an LS1 C5.

Mostly city driving for me turns in 11.8 average.

05-05-06, 03:42 PM
Considering the V is 400 hp, 4000 lbs and has 3.73 gears, I think it does quite well.

Fuel, schmuel. For the next gutless metric four banger owner you meet, thank them for doing their part to allow you to waste the fuel they saved.

05-05-06, 04:04 PM
Fuel, schmuel. For the next gutless metric four banger owner you meet, thank them for doing their part to allow you to waste the fuel they saved.

:highfive: I like that.

05-05-06, 06:34 PM
gutless metric four banger owners
yeah, especially thank those priapusses, i mean prius cars.... i just love to see them putter around.

05-05-06, 07:59 PM
pish posh... 20.8 mpg 1,200 mile round trip to Sears Pt...

now on the track.. 4.7 gals in 18 minutes.. but what a great 18 minutes...:highfive:

V Amazed
05-06-06, 02:40 AM
I got 16.8 mpg on a 6 hour drive from dallas to kansas. Normally i get between 11 and 12. I fillup a lot. :burn:


05-06-06, 01:23 PM
I get just under 21 mpg with 60% of my driving in the city.

05-06-06, 06:55 PM
14.8 city, 18.9 on a ride to ATL & back from HSV yesterday.