I don't know any specs on these motors. hp.torque mileage or anything. I';m new to Dodge. Which motor gets the best mielage? What are the hp ratings for both.

Shawn

 

If you have the money get the hemi! Another 100 hp and 75 torq over the 4.7. The 1-2 mpg the 4.7 gets over the hemi will be gone if you lift it, also if you lift it and put big tires you will lose an insane amount of power. I bought the 4.7 and only 3 months later was shopping for a hemi.

 

go with the HEMI, ive had mine for almost a year and love it!! i have a 22ft ski boat and it pulls it with no problem!! cant even tell its there unless you look in you mirror! the new hemi's have the mds and that helps out with the mpg difference, although if your thinking about putting a diffferent exhaust system on it be very carefull in what you get. you can hear the mds kick in and out so you dont want to get a real loud exhaust cause this (unusual sound) will probably annoy you like it did me. i had to change my exhaust set up twice. i have the flowmaster 50series on it now and couldnt be happier!!

 

I have the 4.7 and the mpg ain't great. Certainly not compared to power difference. Get the Hemi.

 

well, i went from the 3.7L to the HEMI... i just got my HEMI last sunday (1 week ago) and i tanked it once, today im tanking it again... but its still under 2-3k miles (the break-in point) but i already notice a difference between the MPG on the 2 from the first couple tanks. the HEMI is def. getting better MPG. so witht hat said, the HEMI should be doing better than the 4.7 too!

 

I don't have experience with the 4.7 but the last truck I had was a Ford with the 4.6 v8 I bought a 07 QC
4X4 Hemi and it blows away the 4.6 for fuel economy one trip I got 22 mpg,average about 18 combined
could not be happier.

 

if you lift anything you will lose insane amounts of power, depending upon the tire size you go with. thats what gear swaps take care of. look at all the jeeps, rangers, blazers, and samuris out there that are lifted with big tires. they dont have any problem pushing them with their small engines because they have been regeared.

that said, go with the hemi. youll be happier, and mileage will be about the same, if not better with the hemi.

 

Torque in the important 1500-2500 rpm range
is much greater on the 5.7 Hemi V8 than on the 4.7V8

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

for the 5.7
http://www.hypertech-inc.com/dynodgtrk.html

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


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.

See post number 37 in this older thread

https://dodgeforum.com/m_665489/mpage_2/key_/tm.htm

 

My son has an 03 4.7 w/355 gears, the best he's done on the highway is about 18.5 @70 mph.
My 02 4.7 2/392 gears get about 18 hwy and 11.5 city average. I'd love to see how theygot over 20 mpg.
Going downhill with a tailwind no doubt.. Actually, on one of the forums, some guy was getting over 400 miles to his tank, averaging 60 mph (less than 2000 rpm's). I noticed that they didn't mention if it was a standard cab or a quad.

 

ive gotten 19.2 in my 4.7 with 3.92 gearswith a/c on low, windows up, cruise set right at 65 traveling on a flat highway (I10 into louisiana) for about 2 hours. my dad has gotten 22.1 in his old 4.7 with 3.55 gears, a/c on low windows up travelling through the hill country with cruise set exactly at 65. so it is possible to get over 20 in a 4.7, but id still go with the hemi. my dad just got one maybe 5 days ago and its already getting close to what he averaged with his 4.7, and its still in the break in period, so it will only get better. with his 4.7 he average right under 16 mpg with a combo of city and highway. so far driving that same route with the hemi, he has been getting right under 13. after it breaks in he should be averaging about the same.