17.5 - 18.0 with mixed driving. I put 11K miles on the truck since December. I have an hour commute (1/2 there, 1/2 home) everyday and a lot of it is highway. I have noticed that it goes down to 16.5 - 17.5 when I'm running the a/c (been hot). I know the a/c causes more drag on the engine, but I was suprised at how much...

 

im not sure if the MDS is active on the current Durangos w/ the hemi, but i believe(i heard this from someone so i dont have any confirmation on it) running the A/C disengages the MDS feature which would explain why there is such a big difference.

 

I always have the AC on and still get the ECO sign on when i'm cruising without much load.

 

ok then either it has been changed or the guy i was told this by has a problem with his MDS system

 

I'm averaging 20-22 with the v6. I do a lot more city driving than highway, and living at the beach, rarely use the a/c. We traded in my Altima for the D, so obviously the gas mileage wasn't a deterrent for us.

 

I could be totally wrong, but I don't think the "Eco" has anything to do with the MDS and when the hemi shuts off. I have a V6 and it has the Eco sign as well. Where as my husband's ram with a hemi doesn't ever say Eco, but the MDS kicks in on that....... Just my 0.02 :-)

 

You are right. This is from the owner's manual:

"The FUEL SAVER MODE message will display above the average fuel economy in the EVIC display. This message will appear whenever the Multi-Displacement System (MDS) (if equipped) allows the engine to operate on four cylinders, or if you are driving in a fuel efficient manner."

 

I also have a Honda Accord Coupe V6 with Variable Cylinder Management System. Every time the ECO sign comes on, it means that VCMS has shut down 2 or 3 cylinders, depending on load.

 

I have the r/t with the 5.7L Hemi. From home (suburb) to work (city) with lots of start / stopping I get right handy to 14.5. I'm not light on the gas pedal either. When I take trips (interstate highway travel) I get around 19 mpg. I usually run 80-85 mph on the highway. I take the trade off power for mileage knowingly.

 

Yep, in this case, that is wrong. The ECO symbol on the HEMI only appears when MDS is active. If you listen carefully, you can actually hear the tone of the engine change when the symbol appears.