How many miles did you have on your Hemi before you saw your maximum mpgs? Did you ever reach the EPA mileage estimate? 4x4 or 4x2? What mileage do you currently see?

My 2008 Hemi has 1,480 miles and gets 14.5 mpg commuting 75% highway and 25% city. The EPA mileage rating is 13/17 mpg.

Thanks!

 

My 06 QC started getting it's best around 8000 miles. I now have 20000 on it, and getting around 15 mpg in town, and getting around 19 on the open road. Keep this in mind: I drive her really easy. I hardly ever get over 2000 rpm's.

 

I dunno....i've always gotten decent mpg in mine so I never paid attention.

 

Like "Peddler" I get about 17.5 mpg. That's running 65 mph on the commute and very little running around town. However, if I run 63, I get 19 mpg on average (this might have something to do with the MDS mode maintaing at this speed). 7000 miles.

 

many don't realize that at least half of the 'breakin' MPG improvement is from the tread of the tires wearing down, giving lower rolling resistance, not the myth that your engine parts are 'smoothing' down.

The main thing happening inside the engine is that the piston rings are slowly losing tension as heat affects the 'temper' of the metallurgy.
This reduces friction of the rings against the bore walls.

I would say you get 75% of the 'breakin' benefit by 30,000 miles

Car and Driver's long term road tests can show how the
MPG (and acceleration) improves with miles:

http://www.caranddriver.com/reviews/...term_road_test

http://www.caranddriver.com/reviews/...term_road_test

http://www.caranddriver.com/reviews/...term_road_test

 

Yeah my HEMI gets the actual mileage on the window sticker; 14MPH!
Just kiddin' with ya... mine is a Magnum SRT8!

 

Mine has 78,000 miles on it, and still only gets about 11.0 mpg. Hardly driven hard, maybe 2100 rpm at max most times.

 

that might be part of the problem. open her up once in a while, she'll thank you for it.

Engines do not like ALWAYS being at a low rpm with low load. Run the thing hard a couple times so she burns up some of the crud inside.

 

Learned from my 07 after changing the exhaust and adding a cold air intake system my MPG went down to around 13.5 – 14.0 mpg. On my new 08 with everything stock I have been averaging 19.2-19.6 mostly 85% highway.

According to my dealer when I complained about the loss he stated when you change the exhaust out it removes back pressure the Hemi needs for the MDS to work properly

 

in the "old days"
you could go to wide open throttle and high rpm
ocassionally
to 'burn out the carbon'
but today with the PCM computer programmed
to drop the air to fuel ratio down to a very low
10.5 to 1
at full throttle and high rpm
this will build up carbon rather than burn it off

you can test this yourself pretty easily:
clean up the insides of your exhaust outlet,
then begin going to full throttle and high rpm
runs for a day or so,
then inspect the black soot that will have
deposited again in the exhaust outlet

If you are intent on 'burning off the carbon'
you will have to add enough percent of E85
to your gasoline to lean out the WOT setting artificially
.... but there is a detonation danger
that is not entirely canceled by E85's high octane rating