I've been driving the Tahoe for a week or so and I'm not so convinced on the Dispacement on Demand feature. With about a 50/50 split between city and highway driving, I'm averaging right below 14mpg. Furthermore, there's a display that shows when its in V4 or V8 mode. The only time it goes into V4 mode is when going downhill. On flat roads, it still need V8 mode to maintain speed. Now its been my experience that when letting completely off the throttle, like when your coasting downhill, the car cuts most of the fuel supply to the injectors anyways. So, is there really any significant benifit with DoD or is this just a marketing gimmick?

 

How fast are you cruising at?

 

I will say one thing...my Hemi with MDS is a friggen pig. I've averaged about 90% highway driving this first week with my 300, and doing 70 on the highway and not passing 2,500 around town (basically driving like a Prius!!) I'm averaging 19.5...I was up to 20.7 before doing around town driving earlier. For a 17/25 car? That isn't being driven hard AT ALL? It sucks...literally.

Otherwise, the car is sweet But I can drive the GP like I stole it, and average 23 easily with a 50/50 mix...so I am NOT impressed with Hemi gas mileage at all...

 

I suspect that when the Tahoes get the 6-speed autos, DOD will become more flexible and able to kick in more often, but as mentioned... it's a simple equation of if your vehicle needs enough power given your current throttle input, wind resistance, gear, etc as to whether it can run more efficiently on 4-cylinders or 8.

Try cruising on the highway 10mph slower next time; even if you don't want to always have to go slower, just try it as an experiment.. see about what point DOD stays on on a flat surface without much if any headwind and consider if that'd save you enough fuel for you to slow down your driving enough.

But like I said - I'd probably not buy the GMT-900 until they got the 6-speed auto in there, for that reason among others.

 

Isn't DOD only supposed to supply an approx 4-6% gain in fuel economy?

Even at an expected 20mpg for a non-DOD engine, the gain would only be around 1 MPG anyway.

While an improvement, I don't know that it's one that would jump out at you as much as just pay off over the long haul.

 

Doing even 5 MPH slower in the 300 netted me an additional 2 MPG when cruising on the highway...it went from about 19 to about 21 slowing from 75 to 70...

 

I always heard 10-15% when the tech was first making its way into vehicles.

 

I think that was for the 6 speed autos, they were 4-8% vs. a 4 speed. DoD was over 10%

 

For reference... this claims 6 to 8% gains with DOD/AFM...

http://en.wikipedia.org/wiki/Active_Fuel_Management

 

I can slow down to 60mph (you get run over at that speed on Hwy 40 in the morning rush) and it still needs V8 mode to maintain speed.

 

I am getting 17mpg in my GXP. Doing the same driving in the Comp G I get 21-22 MPG.

I have over 1000 miles now and it is not getting better...

I am now angry...

 

Our AWD Trailblazer SS without all the newfangled technology and 4.10 gears is averaging 12.63 MPG over the first 3500 miles ... and that's with lots of 65 - 70 mph highway driving.

But how to do measure "grins per gallon" .... it's off the chart in that category.

 

With about 7K on the clock my wife only gets about 13-14 MPG all city driving in her GXP.

 

I get about 33mpg 50/50 mix driving, so I guess that means I win!!! Oh, wait thats in the Neon... I knew there was a reason I keep that thing around, I don't think I even want to know what the GTA gets, I'll know once I start driving it more regularly.

 

I would say it's a lot like CAGS. It does what it's supposed to for the EPA tests, but in real world driving its benefits are lot less real (which is okay by me).