..My car went on a week long trip and just got home. Driven by my wife (someone has to work around here) and my father in law (who now has more time in it than I do) to calif. and back. they don't understand ANYTHING about how the car works other than the basics but it still returned 19 mpg at 85 with the cruise control doing the driving. It now has 2400 miles on it (and about 1/2 ton of seirra nevada dirt). Picked up a really nice chunk of road fod and had a leaking tire when it got home but otherwise no worries from it at all. I sure hope I can figure out a way to wash it without scratching it, I think a serious detail and wax job is in my future!

 

Wow! That is very impressive for running at 85mph. I have run my civic hybrid at 85 for long periods, and I must say, the mileage is way down. I have dropped into the low 30's for mileage driving in the mid 80's. The car is rather quiet, but whiny at those kind of speeds. I bet that Tahoe is quiet and turning some seriously low RPM's. What speed will it run on 4 cylinders?

 

[quote= What speed will it run on 4 cylinders?[/quote]

I haven't been able to drive it on the highway, my wife is the one who took it on the trip and she is really in to tech aspects of the car so all they did was put the cruise control on.
My father in law (ex marine) was very impressed and told me so! I had to check his ID to make sure it was him! I have seen 4 cyl mode on the freeway the few times I have taken it out and typically they were straight and level at 70 or so but I haven't had a real trip in it myself yet.

 

Not too bad @ 85

 

So far I have not been able to beat the mpg's of the cruise control. It seems to be better at keeping the economy gauge at the middle or close to it even on mild uphill drives.
It is very easy though to let the vehicle stay on 4 cyl. Just accelerate to the speed you want and engage your cruise. Then drop your speed in 1 mile increments with your cruise until the engine switches over. From my experience, anything past 64mph, it will not switch to 4cyl unless it is really flat.
In time you will know how to ease up with your foot to trigger the switchover.
When I was in Jekyll Island, I drove around the place at night and kept my cruise at 38 to 40. I was the only car at the time and I was enjoying the place and was averaging 40mpg. When I kept it at 24mph, it was running EV only and switching on to charge the batteries only and then going to EV again. But I never got the estimated 4 mile range on EV ever. On average, I think I only got 24mpg doing that.

 

Those numbers are pretty good. Too bad it cannot stay in 4 cylinder mode with a bit more speed, but my Civic drops dramtically in mileage at speeds over 65 on flat terrain and inclines.

A vehicle with the kind of mass the Tahoe has that can get anything over 30mpg at any speed is impressive. My wife never gets our Dakota above 60mph and she has yet to break 19mpg. She drives 150-180 miles a week, I end up filling the "black hole of fuel" between 270 and 330 miles. with about 20 gallons on average. Sometimes more, sometimes less. Considering the darn thing is driven with an extraordinary light foot and only has a 4.7 litre engine, I think it should fair better.

Sounds like you were moving faster than golf carts while in EV mode. I bet some sort of software will come out in the next couple years that will allow for more speed and range from your battery or a new system will be available to make it work better. Either way, it is way cool!

After reading your posts, I am really looking forward to driving the 2 mode Silverado. I won't be buying one until the Volt hits the market. My plan it to purchase a Volt and 2 mode Silverado at the same time. We need a truck. We do not need an SUV, but we need a truck. We all have different needs. I max out or Dodge towing as it is. The hybrid Silverado has a lower tow rating than its counterpart, but I believe it had something to do with the engine cooling system and not the actual drivetrain.

If I can get 400 miles from 20 gallons in a truck that I will be spending over 35 grand "no matter what I buy", when gas gets expensive again, the price will be worth it to me.

 

ever since I got the new software config it will go into 4v sooner and the engine does not have to be at temp to shut off at stop lights which it did before! now when the temp gauge hits the first 1/4 hash mark it will shut down at stops and its lots easier to keep it in 4v mode longer, although it always starts out in 8v and battery (depending on your right foot of course)
I filled the tank three weeks ago and just drove it normally as I would have with my jeep. The jeep used a tank of gas a week typically. The yukon just hit the 1/2 tank mark today! I have been using the onboard tools (instant mileage, hybrid batt-engine screen)but otherwise I am just driving normally. I am totally amazed at this truck so far, and if it makes 4 weeks on one tank of gas (which is what it looks like to me) I think everyone who needs a big vehicle should buy one!

 

Two short (200 miles in west Texas) trips in the Tahoe this week.
Drove 65-70 and kept a close eye on the instantaneous fuel gauge, working to stay in 4 cylinder mode as much as possible. Totaled 468.4 miles on 17.9 gals.
The average MPG indicated was 24.8 on the DIC (DIC showed I had burned 19.3 gals), calculated an actual average of 26.2 using the mileage/pump. (Yes ... I did top it off completely).
I have 4200 miles on my '09. So far ... it has been flawless!

 

good to hear! I'm starting on week 4 of my real world test on a single fill up. My guage is still sitting on 1/2 a tank---filled 4 weeks ago today. Im going to do a good ole math determination when I fill up next time, and other than paying attention, i'm just using it as I would have my last car. work home errands, no trips at all so far on this tank.

 

I drive too much to go that long without a fill-up
I have seen (at least according to the DIC) that my worst fuel economy occurs in the first few minutes of driving, before the ICE is warmed up. The better economy starts once the engine temp is just above the first tick mark on the temp gage, allowing 4 cyl mode and electric assist. Also, when the outside temps were low (below 30 F) it took much longer to get hybrid or EV mode. the last few weeks have been in the 70s and 80s here, allowing for immediatte us of the EV and hybrid modes after the ICE is at temp.
Also, on the highway, I tend to allow the speed to decay slightly traveling uphill and accelerate on the backside, all the while maintaining 4 cyl mode if possible. I think the cruise control is too aggressive to allow for optimum economy.
Thanks for your updates.