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07 V6 seems very thirsty

3404 Views 32 Replies 17 Participants Last post by  treslados
Just picked up my 07 V6 AWD this past weekend. Drove about 300 miles home on the highway and barely broke 18 mpg. I wasn't driving that fast (never more than 75 with long stretches of 70 mph) and the weather was fine.

I know this thing is no Prius, but 18 on the HWY? EPA is saying 21 MPG and I've always beaten HWY EPA on any car I've owned.

Car runs fine, etc, no check engine light. It does have the factory sport package with the 20" wheels. Could these hurt mileage that bad?

Considering a preemptive spark plug and O2 sensor change to see if that helps matters.

Or, should I just accept it as normal?
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I have an 09 V6 RWD and am not overly impressed by the fuel mileage. In fact I doubt I'll meet let alone beat the Highway rating of 23. This would be my first car in decades that I couldn't match or exceed it's rated highway ratings.

I'm even running my tire PSI a few pounds over the door sticker and drive with a very light foot.

I don't think you'll find any extra fuel mileage in this vehicle absent slowing down some and driving like there was an egg between your foot and the pedal.

BTW I did manage to increase my city mileage some, (to 16.3 MPG real world hand calculated) but it takes a lot of effort and I piss off more drivers because I accelerate so slowly and start coasting when I see a red light.

My next real opportunity to verify my real world highway mileage will come when I take the tribe to Indy in July for the Allstate 400. I was hoping to get 24 to 25 MPG but have since lowered my expectations to 21 to 22. Anything less than that will cause me to rethink how long I will keep this vehicle since we all know fuel prices are going back up.

As a point of reference my lightly modded 06 vette easily gets 30+ MPG (highway).
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I don't think your mileage is normal at all. I have an AWD North Star V8 that is getting better mileage than your V6 and I am using Florida gas (10% ethanol). Perhaps some of the V6 owners will chime in and share their MPG numbers.
Nope... that is just what the thing gets!

It will improve as you put some real miles on it, but don't expect much more then 21 Hwy.

MPG is one of the things that killed the sales of these things... However, know that the MPG from most of the competition isn't all that better.

If you want Mileage - buy a Hybrid like Prius or or super-sub-compact like a SMART or Cooper.

Hell, my 05 Customized Mustang GT V8 with 330RWHP gets 23Hwy and 17city WITH me jumping on the gas from every stop light! But I can't put 10 bags of Mulch in the trunk of my Mustang!
It doesn't sound too far off. My 05 RWD gets about 21-22 at 75MPH. AWD will take a hit.

I can get into the mid-20's if I would keep it under 70. But I can't! ;)
I have an '08 V6 2WD.
YTD I have gotten an overall 18.5 MPG, all driving done in and around the streets and freeways of North Dallas; with no highway trips, and no speed above 65 MPH. To me, this seems to fit the advertised 15-22 MPG exactly.

I have 3 comments about MPG.

1. Yes, the AWD will rob at about 1 MPG, and the 20" wheel package will probably rob 1/2 MPG (particularly around town) due to additional weight to get moving, and wider tread with more rolling resistance.

2. Speeds above 60 MPH will kill MPG on an SUV. These are blunt instruments with horrible aerodynamics and not very tall overdrive gearing. Going 75MPG will probably drop mileage 4 MPG vs going 60.

3. So, based on that, I would suspect typical highway mileage on an AWD with 20" wheels, doing 75 MPH, would be 17-18 MPG.
So, yours seems to be just about right.

Wind resistance is such a killer as speed increases. As stated above, my Corvette also gets tremendous MPG, and doesn't seem to lose much even at highly illegal highway speeds. But it's super slick, and has a small frontal area to boot.
On the other hand, I had a PT cruiser with a tiney 4 cylinder that wouldn't break 20 MPG when I drove it 75 on the highway.

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I am getting about 20 to 21 mpg using 89 octane in my AWD N*, 20" wheels tires and tire pressure around 34. The N* has a 6 speed and a fairly tall 6th gear. The V6 has a 5 speed. While cruising at 70mph my RPM is around 1600-1700 i think. Check and see where your RPMs are at when your cruisin at 70mph. Make sure your air filter is clean, that can make a small difference too. I haven't seen a huge difference with accessories on or off, meaning A/C, Radio, etc...

Best I ever got was a 95% highway trip 300+ miles almost no elevation change using 89 Octane, I got 22 mpg
We have an '08 V6 AWD with the 3rd row and UV roof and we consistently do better than 20 mpg on the highway. Of course, we rarely hit 75 mph...
I have an 04 V6 AWD with no Ultraview and the standard 17" rims size. At normal interstate speeds (75 mph) I've been averaging 22-25 mpg. In city traffic it drops down to about 15-18 mpg. I have discovered I get better mileage at 78 versus say 73. And I've also noticed the wind has a definite effect on the mileage. For you to get 18 on the HWY that must have been to hell of a head wind.
06 Nstar FWD with no sunroof. In the city, 12-13 MPG. Hwy below 69mph-22mpg above 78mph-25 MPG. Folding down the 3rd row doesn't help. Yes, compared to pick ups and large SUV the SRX does hold it's own. However, there should be some kind of mod, like different injectors, a different chip, something.
V6 with 36lbs in the tires I can get 22 Hwy very consistently even with 30K on the air filter. Yes, I just bought one.
My V6 RWD has an average of 21-22 on the higway, average speed is 75mph. In the city, it drops to 16mpg..that hurts. I'm using a much higher tire pressure than recommended: 2,7 bar(29 psi). But it seems that doesn't affect the mileage much, this engine and it's body simply can't go under 21 mpg.
06 Nstar FWD with no sunroof. In the city, 12-13 MPG. Hwy below 69mph-22mpg above 78mph-25 MPG. Folding down the 3rd row doesn't help. Yes, compared to pick ups and large SUV the SRX does hold it's own. However, there should be some kind of mod, like different injectors, a different chip, something.
Wait... you get 10% better MPG going 10 mph faster? Sorry dude, that's just not possible

Second... if the seats are INSIDE the car, why would folding them up down or whatever make any difference?
Both my '04 and '07 SRXs V6 RWD record basically identical mileage.
There are 2 things you have to remember about these vehicles.
1)it is a CUV with a lot of frontal area.
I drive 80-81mph. 20.4-20.5mpg is the best it will ever get at these speeds.
If you are faced with a head wind i have seen as low as 18.5mpg at the same speeds.
But as soon as you slow down aroound 55-60mphyou can record 28mpg no problem.

2) gearing: the rwd has 3.73 gears and the AWD 3.91s + another 150-200lbs of weight.
5the gear is only a .75 not a .67 that the cars with 6spd autos have.
The V8s with 6 speeds can pull very close numbers to the v6s.

Gas mileage for me in town is about 15.3mpg.

Keep your speeds down, keep ALOT of air in the tires and it will pull okay numbers.
If you want better mielage in the V6 put 3.23s in it but you will have weaker acceleration.
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mattias, you should have more than 29psi in the tires.
15.3 city... damn... I'm no longer going to complain about my 17.5mpg City.
Ah so... 3.73 gear in da rear. That explains the MPG! Also explains really fast feeling when tromping it.. even with the third seat folded up. The SRX is a hot rod. Gonna have to run it down the strip for a 1/4 et.
Soo... I wonder how available the 3,23 gear. Also, is it possible to gear the tranny?!
a word about the 3.73s.
keep in mind that the tires are tall on the SRX so it is not quite the same as having 3.73s in a 60s or 70s musclecar with 25" tall tires.

One of the reasons the V6 SRX doesn't get better mileage is that 5th gear is a .75 overdrive not a .70 that was in the 4 spd autos or the even taller .67 that is in the new th '10s or the later V8 SRXs.

If you put a .67 overdrive in the V6 rpms would dop by 200rpms at 80mph. Worth a least 1 mpg.

As far as putting the V8's 3.23 rear gears in a V6 you woul probably lose .5second 0-60 and it would hunt for gears on the highway going over hills because there probably wouldn't be enough torque to pull a 3.23.

If you were running 2000 rpms with the 3.73s you would only be running only about 1700rpms with the 3.23s.
Soo... I think b4Z has an actual solution.
In theory, one could increase the average MPG of an 06 SRX N-Star with the 3rd row seat in the powered down position by replacing the stock rear and tranny gears with a 3.23 rear plus the .67 in the tranny?
And if so, I then wonder whut be the over the counter availability of the parts.. do they just slip in, can the tranny gear be replaced without removing the entire trans from the car, does changing one part mean having to change a bunch of other parts, re-mapping the computer chip stuff, different injectors???
mattias, you should have more than 29psi in the tires.
I believe I converted it wrong, 2.7 bar is 39psi. I believe Cadillac recommends 33psi?
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