Some random guy told me the other day his 8 gets better mileage than his 6 did. The only reason I can think of for that is with a V8 one can get a smaller rear end, rather than the big one I'd need with the locking rear in the V6. Does anyone have real world input for me to consider before I buy in the Spring?

Thanks for any help,

Jason

 

I have an '03 QC 2wd with the 4.7L engine and my real world mileage is 16-18mpg everyday, going back and forth to work and round town. I can get almost 22mpg running on the interstate at a steady speed (65-70mph). Those numbers are from the idiot overhead computer, but they seem pretty close. My dad had a first gen 3.9L V6 and he pretty much always got 18-20. If I recall when I bought mine, the window stickers between the V6 and V8 were either the same or 1mpg different for 2wd models. Hope that helps.

 

these trucks are pretty big and most people with v8's tend to get better gas mileage then the ones with the 3.9 v6 because it doesn't take as much to get going and keep it moving where as the little v6 has to work harder and your in the higher rpms more however with the new 3.7 im not to sure i would guess that you would probably be able to get better gas mileage with one of those then the v8 but not by much. my truck with the 4.7 and 5 speed gets between 17-20 consistently driving to and from school which is 140 miles and then mixed city/country driving into that.

 

The sticker numbers (not real world) say the V6 gets 1 MPG better than the V8. I avg. 17 in the city and 19 on the hwy, but I have the 3.92 rear end.

 

Yeah, pretty much the sticker says V6 is 1 mpg better, but the real world usage is that they are about equal of the V8 does a bit better because it has more power lugging the same weight around.

 

when i looked at the v6 vs the v8 the v6 said 15 cty 19 hwy and the v8 said 15 cty 20 hwy both of the trucks were quad cab 4x4


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+

Jay,The V8 has a whole different trany VS the V6.

Blu_

 

V-6 trucks get the 8-1/4

4.7 trucks get either 8-1/4 or 9-1/4, depending on options

 

below is an old post with more info on the subject of
5.7 vs 5.7MDS vs 4.7 vs 5.9
fuel economy
---------------
At least this month (Jan 2007)
Chrysler has been offering the 5.7V8 with MDS as a
"no cost upgrade"
over the 4.7 on Rams
and pointing out to customers that
the 5.7MDS has better EPA MPG test results by about 1.
When evaluating this, keep in mind that you are comparing a 5.7V8 running on 4
cylinders (and dragging along 4 not being used) at a speed of 55 mph to a
4.7V8 running on eight cylinders also at a speed of 55 mph.

At speeds of 70-79 mph the MDS on the 5.7 Ram will not kick in unless you are
going downhill, or have a wind at your back. Here at higher speeds the 4.7
might regain an MPG edge.

The UAW workers at Mack I/II engine plants in Detroit are feeling this and
worried for their jobs building 3.7 and 4.7 engines:

http://www.detnews.com/apps/pbcs.dll...701300367/1148

Even before MDS was introduced on the 5.7V8
the unmodified EPA lab results were showing
that the 5.7 was within 4% of the 4.7 V8
in fuel efficiency.
The actual test results are available online from the EPA at:

http://www.epa.gov/fueleconomy/data.htm

to see the actual results go to this link:

http://www.epa.gov/otaq/tcldata.htm

These are not the 'Window Sticker' numbers,
these databases have the actual city and highway test results down to a tenth
of a mpg. This makes it easier to compare. Since 1985 EPA has applied a
'fudge factor' to these actual results to get the number that you see on the
Window Sticker. This happened because citizens complained the EPA city and
highway numbers were TOO HIGH compared to 'normal driving'. Next year EPA
will apply an even greater 'fudge factor' because citizens are still
complaining that they can't get at 79 mph the MPG that EPA measures at 55 mph.


If you look at the 2003 year numbers
you can compare the Magnum
5.9V8 to the 5.7V8 (without MDS back then)
and to the 4.7V8 and 3.7V6

3.7V6 2wd had 25.4 MPG highway with 45RFE and 3.55 diff
4.7V8 2wd had 24.2 MPG highway with 45RFE and 3.55 diff
5.7V8 2wd had 23.3 MPG highway with 545RFE and 3.55 diff
5.9V8 2wd had 22.0 MPG highway with 47RE and 3.55 diff

Chrysler's official press release on the 5.7 Hemi said that it was 8-12% more
fuel efficient than the 10 year old Magnum 5.9V8 design. But notice
in the above that in the 2003 Ram pickup the 5.7 Hemi was only (23.3/22) 6%
more efficient at highway speed. This may be because the 545 automatic
transmission has more internal friction when in overdrive (where it has two
planetary gearsets turning) compared to the older 47RE auto that only had one
planetary gearset turning.

For comparing the 5.7 with MDS to the 4.7
look at the 2007 year numbers.

4.7V8 2wd had 23.7 MPG highway with 545RFE and 3.55 diff
5.7MDS 2wd had 25.4 MPG highway with 545RFE and 3.55 diff

Adding MDS to the 5.7V8 at a steady 55 mph improved it by
(25.4/23.3) or 9%
This matches what Chrysler said in their press release about MDS on the 5.7V8
where they wrote the most gains were below 60 mph, with maximum gain of 20%
around 45 mph.

2wd 5.7 Rams will be able to go a little faster in MDS mode and get better MPG
than 4wd Rams because the extra driveline friction and weight of the front
axle loads the engine down more.
=======
Torque in the important 1500-2500 rpm range
is much greater on the Magnum 5.9V8 than on the 4.7V8

See these rear wheel dyno curves
and look at the 'stock' torque numbers for each engine:

for the 5.9
http://www.hypertech-inc.com/dynodgtrk.html

for the 4.7
http://superchips.com/~superchips/prod_imgs/makepdf-822.pdf