WS6 John

iTrader: (2)

Took my wife's 07 Impala SS on vacation to South Carolina a few weeks ago, ~ 870 miles each way.

Car had 5400 miles on it, set tire pressure to 32psi cold, AC on the entire time, used cruise control most of the time, car had a lot of extra weight in the back seat and trunk. Other thing worth mentioning is that a 4 wheel alignment was done before the trip.

On the tanks of gas where we did not hit much traffic, I got the following:
28.3 MPG with an average of 63MPH.
27.4 MPG with an average of 70MPH.

At 75MPH, the gas mileage starts going down significantly. On the tank that we got 27.4MPG, it was > 28MPG until the last 100-150 miles was driven at 75MPH bringing the mpg down by 1mpg.

On the first tank of gas, we average 25.5MPG with an average speed of 43 MPH. We got caught in tons of traffic, but I was still impressed the gas mileage was this high with the traffic.

Since we bought the car, I was questioning how effective the DoD was. In city driving, this car get pretty poor MPG even though it runs in 4 cyclinder mode a lot. This tripped proved to me DoD works very well.

20SS07

Yea between 65 and 70 I get anywhere from 27-29. Doing 80 last weekend i averaged 25.6.

GMMillwright

iTrader: (4)

Interesting. Why'd GM lower the highway estimate to 24 for 2008? It's the same drivetrain, right? I'm considering an SS when the lease on the van is up in the Spring.

hexxLS4

iTrader: (1)

Because in reality most people are going more like 75-80 on the highways....and the MPG really starts dropping off around those speeds.

Anyone else jealous that corvettes can get better gas mileage than us all while having 66% more HP AND no dod? I wonder how the G8 is going to do with the 6 speed AND dod...should be interesting.

One thing I am happy about is the MPG I get around 50mph....thats where this car really shines...I've hit between 30-40 mpg at that speed.

BacknBlack

I average between 23 and 25 mpg with mine....I think we do a little worse cause of the high altitude

someday

GM didn't, the EPA did, they finally changed their test procedures after 30yrs, to more resemble the way everyone drives these days... every car sold here will have lower #'s for '08...

Nacho SS

iTrader: (4)

John, do you run 91 or 93 octane?

Does octane rating have large affect on the mileage?

20SS07

Yea that was all the EPA's doing. Doesn't mean the car is going to perform any different than it did in '07, just a better overall picture of how people drive. They also added in things like testing with the AC on now etc.

WS6 John

iTrader: (2)

87 octane. (running and hiding now)
Being that it is my wife's car, and she does not drive it hard, she always puts 87 into it. The dealer had convinced her that higher octane is not required.

Nacho SS

iTrader: (4)

Lol...just kidding.

There's no shame if you don't push the car hard...It will just knock and rattle and sputter...

Kazmaniac

I switched to 89 octane a few tank fulls ago and haven't noticed the difference in performance - my car still does 10-15 under the speed limit following a minivan in heavy traffic.

My G/M is now at 19.3 lifetime w/ 34,000 miles. 85% of the miles are highway based, at 74 mph in cruise.

Agree that mileage falls off significantly above 65.

Mark IXZD 150

iTrader: (1)

There may be some truth to that. If a car isn't driven too hard 87 would probably be fine for easy driving. If it starts to get knock, the computer will retard the timing and relearn to make it run better on the 87. Someone correct me if I'm wrong.

I've occaisionally put 89 in my car because I just couldn't get myself to put the 91 in there at times when the prices shot up so high earlier this year. Most of the time I do use 91 but often wonder if I'm wasting money. Most of my driving is back and forth to work in traffic and the only time I use the power my car has is when I need to shoot past some retard in my way.

Sint3k

i get about 450 miles per tank when i'm driving 60mph non stop with cruise control. Driving without cruise control at the same speed will lower your MPG just do to the natural feathering of the throttle up and down hills. I use 93 Octane by the way. The car has never seen 87

WS6 John

iTrader: (2)

I'm not sure why GM recommend 91+ octane in the Impala 5.3 with only 303hp, but the Tahoe with the same engine has 320hp and requires only 87 octane. My guess, we probably have 299 horsepower with 87 octane, but GM wanted to advertise 300 + horsepower, so 91+ octane is recommended.

I have never heard the car ping. I would hook it up to autotap to see if it got any known retard, but my version of autotap will not run on this car.

The impala has never had anything but 87 octane in it. When we picked it up from the dealer, I asked them what grade of gas they put it. They put in 87 octane.

I would say that it will give my TA a good run for the money, at least before I put the twin turbos on the TA. The TA always get 93 octane because it will ping with anything lower. The TA even pings sometimes when I have an old tank of 93 octane.

heavyft

I averaged 26.4mpg while cruising all highway at 85mph on 93 octane.

Notime383

iTrader: (6)

I use 93 Octane and drive my Imp to work once a week about 130 miles round trip mostly highway, I go about an average of 70mph, 2000rpm's, and get 20-25mpg, I don't drive hard I'm in 4cyl mode about 40% of the time!

20SS07

A buddy of mine with an 06 Imp SS has always used 87 with no problem. I've never used 87 in it I used 89 when I first got it and at about 5,000 miles started using 91+. Haven't really noticed any difference. I had been averaging about 19.8 MPG's throughout the summer however my last 2 tanks of gas have been just over 22 with the same type of driving I had been doing all summer. About 20 city miles throughout the week and about 200 highway and 100 city over the weekends. Dunno why I went up with the same kind of driving.