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Discussion Starter · #1 ·
I'm starting this to find out if I can effectively up my horsepower and my gas mileage..By using machine work and/or bolt-ons. Any suggestions would be greatly appreciated! I have a 98 ram 1500 w/360 4x4. My goal is 15-16 mpg and as much horsepower as I can make..or am I just nuts? :huh:

1,733 Posts
This was written for second gen Rams and has been partially modified but needs
to be re-written for 3rd gen Rams
{please point out broken links}
but the basic principles apply.

With the dual sparkplugs and deep-in-block knock sensors the 5.7 might really
benefit from a special design piston that raises compression ratio and shifts
the combustion space over toward the exhaust side.

Aerodynamics is even more important on 3rd gen Rams to improve highway mpg
because they have gotten taller, wider (increases frontal area) and blunter
(worse in engineering term called Cd or 'coefficient of drag).

old post:

Ram Pickup MPG improvement discussion :
{last modified 05-08-05}

Switching to synthetic lubricants - - engine oil, diff, Amsoil C+ Mopar-spec
transmission fluid, and syn greases in wheel bearings is good for 2-5% MPG
improvement. That is only about 0.5 mpg but every little bit helps.

Larry Shepard writes in the 'Magnum Engines' book published by Mopar Perf that
running engine oil and transmission ATF levels 1-0.5 quarts below the 'add'
marks on the dipsticks can increase MPG slightly due to less oil drag. If you
do this, you must check levels very frequently to see that you don't drop oil
levels even lower into the 'danger zone.'

Another 'non-sexy' but effective way to increase mpg is to keep an electric
block heater on while the truck is parked. The Dodge PCM computer richens the
mixture until the coolant temperature gets to 147 degrees F. By keeping the
block warm the engine goes into the more fuel efficient 'closed loop' control
sooner. This MPG improvement works best on trucks that do short trips. At 8
cents per kw-hr electric rates, running a 700 watt block heater for 8 hrs
costs 45 cents.

As others have said, a hard tonneau can lower the aerodynamic drag. I
installed a ARE hard tonneau and found it was good for about 1 mpg
improvement. Ford says that a soft tonneau is good for +1 mpg on the F150 and
tried to get the EPA to allow them to add this to their highway MPG result by
re-classifying the tonneau 'standard equipment.'

This Fibernetics hard tonneau has a 'Roofline Extention Spoiler' on the back
that might help MPG a bit more than a conventional design. Here's a view of
the rear spoiler, but on a F150:

There is an interesting student project on a aero improvements tried on a
Dodge Ram model truck several posts down at this link:

or go directly to the stored old pages here: ffner/did.htm
and onneau.htm

Note that the students found that camper tops and removed tailgates hurt, but
tonneaus and lowered tailgates helped slightly.

It is possible that a 2inch front/4 inch rear drop on a Ram suspension could
improve the aerodynamic drag. There is some evidence that on a 1996 Indy Ram
this improved the Cd by a few hundreds.

The 3rd gen body on the SRT10 Ram uses a 4/6 inch lowered stance, a rear wing,
tonneau, and perhaps partially block off of the 'too big' radiator grille to
lower its aerodynamic Cd from the 0.50 of the stock 2500 Ram to the SRT10's
value of 0.45

Bug shields at the front of Rams nearly always hurt MPG.

The Dodge Ram Diesel that set the Bonneville speed record had 'Mooneye' wheel
cover discs. These are supposed to reduce aero drag by 1-2% but hurt brake
cooling. I also notice this Ram had mirrors and wipers removed.

I have recently had some aerodynamic success with home-made little aluminum
tabs called 'Wheeler Vortex Generators'. I mounted 5 just behind the side cab
windows, and another 5 just in front of the rear brake lights. These improved
my coasting speed down a 6% grade hill by 2 mph, and also improved MPG at a
steady 70 mph by 1 mpg.

I had previously tried this product on the roof of the truck, but it did not

The vortex generators I made were cut from 5 inch by 7 inch aluminum
'flashing' from Home Depot. You cut the flashing into 3 and 9/16th inch
circles, and then bend the sides up to form the 'wings'. A circle of course
has 360 degrees. The front of the wings take up 107 degrees of the circle,
and the back takes up 22 degrees. The finished product looks like this:

but without the magnet backing. I used 3M 'Super Strong' outdoor mounting
tape from Target to stick the vortex generators to the truck's sheet metal.

I am still testing with the Wheeler Vortex generators. I have tried bending
dimes into tiny ones for the mirrors - but no measureable change. I have also
tried little 1.5 inch ones on the bottom of the Ram airdam - felt more stable
but no measureable change.

Sparkplug and ignition advance changes. I did a careful test run of 311 miles
after indexing sparkplugs in a 5.9V8 and
got a 4% improvement. That could be random variation but I suspect not. To
index the plugs, buy 16 instead of the usual 8 and choose plugs that tighten
down so that the gap points toward the V of the engine and the ground
electrode is on the fender side. Return the 8 plugs you don't use to the store
or give them to another Ram owner. This puts the metal post of the ground
electrode over against the metal wall of the cylinder head where it does not
block the growth of the flame. See this webpage for a view of the combustion
chamber. In the picture the top is toward the fender and the bottom is toward
the center V of the V8 engine:

There is an article with several good illustrations at this Phord site:

On a 5.7Hemi, it is very probable that by re-arranging the stock 16 plugs to
their best position you could achieve indexing without buying more than 4-6
additional plugs at most, perhaps none at all.

Tests of the Bosch+4 sparkplugs at 60 and 70 mph highway speeds with 87 octane
gasoline found no improvement - actually a slight loss - on a 1500 1995 SB CC
Ram with 5.9V8 AT. A further test of the Bosch+4 sparkplugs with one of the
electrodes closest to the exhaust valve cut off (making a Bosch+3) also showed
no MPG gain.

There is controversy about MPG and thermostat temperatures. Pure theory says
that cooler air intake temperatures give improved MPG because cooler air takes
slightly less hp to compress, but hotter oil on cylinder walls gives less
friction to
the piston rings which can also mean better MPG. Theory also predicts that
hotter block walls and cylinder heads will absorb less heat from combustion
and permit a greater 'push' on the piston.

Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg. Other Dakota owners reported no
mpg change or a loss. Four Wheeler magazine reported +0.8 mpg gain with a 192
to 180
deg thermo swap in a 454 Suburban. Marlan Davis has reported that all things
considered, fuel economy is better with coolant at 210 degrees F.

My own experiments with failed thermostat that cracked and stayed open at
around 140 degrees, 180, 195 (stock) and 205 thermostats showed no measureable
improvement in MPG at steady 60 mph highway cruise on a 1995 5.9V8 Ram CC
shortbed. The 180 degree thermostat also did not reducing pinging, nor did
the 205 thermostat increase pinging. The cracked thermostat that stayed open
at about 140 did reduce pinging.

Note that on 4.7 and 5.7Hemi engines the thermostat position and function has
been totally
redesigned to control the coolant in, rather than the coolant out
temperature. The 5.7V8 also has a closing bypass feature.

The Fuel Economy Calculator from Performance Trends software predicts that a
change from a 195 degree thermostat to a 175 worsens MPG by about 0.20 at a
steady 70 mph.

Undersized crank pulleys can increase MPG slightly and are relatively cheap.
Some report an additional undersized alternator pulley is too much for the
street truck that may have to idle a long time without enough rpm to charge
the battery. I haven't tried one yet - but did much the same thing with a diff
gear change.

I changed out my original 3.55 differential gears to some $75 new-in-box but
20 years old Mopar ones of 3.21 ratio in hopes of better mpg. I got about a
0.5 to 1 mpg improvement at 70 mph. I had hoped for more. Quarter mile times
got worse by 0.75 second. My 5.9V8 now accelerates about like a 5.2, but has
about a 5 mph increase in top speed in 3rd gear as the gear ratio is more
matched to peak hp.

Note that on the 5.7Hemi with the new auto trans the overdrive gear ratio was
made "taller"
to 0.67 from the old 0.69 at the same time that the 17 or 20 inch wheels &
tires were made larger in diameter. This has an effect like changing from 3.55
to 3.21 in the experiment above.

A less restrictive muffler can help on a Ram. I switched to Walker's
'QuietFlow' type and gained about +1 mpg and dropped 0.2 seconds from the
Q'mile. The QuietFlow is as quiet as the stock muffler. Walker also owns
DynoMax, and the tech on the telephone told me the DynoMax is about 10% less
restrictive than the QuietFlow but much louder. But after 15,000 miles, my
QuietFlow began to rattle and I had to squeeze a dent in it with a large
C-clamp to stop the noise. So far it is still quiet.

I later replaced the QuietFlow with a 30 inch long 'straight through' DynoMax
UltraFlo Stainless Steel 2.5 inch in, 2.5 inch out.

part number 17298 that cut the wide open throttle exhaust backpressure from 7
psi to 5 psi. This reduction in backpressure only yielded a gain of about 0.2
MPG. The Ultraflo 17298 was a little louder than both the stock muffler and
the QuietFlow, but just barely. I later had to add an additional 16 inch long
UltraFlo as a tip to eliminate a 1700-2000 rpm resonance when cruising in

I also moved my exhaust outlet to face rearward and installed a megaphone tip.
A rear facing exhaust oulet has a very very small 'jet engine' push to
it - notice most cars exhaust backwards - but trucks that pull trailers need a

side exhaust to safety exhaust carbon monoxide away from where it could cause
a deadly build up inside a camper.

On the 5.7 Hemi Rams, the exhaust pipe sizes, muffler and resonator are
already fairly low restriction.

Headers are heavily advertised as helping MPG - a psychologically trick that
helps create sales - but in most cases headers don't do much because the
primary pipes on them are too short. Many headers are put on at the same time
as new less restrictive exhausts - and the header gets the credit for what the
bigger muffler actually did.

Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely helps MPG. Raising the air pressure by 15 psi to the max 70 psi in
Goodyear Wrangler HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
and a weekend mudder wide tire set.

Consumers Reports is the only organization I know of that tests for rolling
resistance of tires.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."

In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:

Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A

The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051

A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03

The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one
of the few worth while things CARB has ever done in my opinion

The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It
is probable that if a manufacturer makes available a 235 85 R17 tire in Load
Range E it would be lower rolling resistance than the stock tires and might
improve MPG by 1-2 at 70 mph.

The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'

A carefull MPG test of a 1995 1500 SB CC Ram with the 5.9V8 AT (3.21 diff)
with and without the radiator fan showed a 0.8 MPG improvement without the
fan. No overheating occured in this steady 70 MPH test run over 212 miles.
There was also no sign of overheating at stoplight stops or city driving in
mild winter temperatures. Several Diesel Ram owners have posted that they can
run without a fan in winter and gain 0.5 to 1 MPG.

With the electric fan & clutch fan combo on the 5.7 Hemi Rams it is probable
that the clutch fan
could be removed for all but the hottest weather or towing service.

Another MPG test over the same stretch of highway at a steady 70 mph showed
0.7 MPG worse without the Ram's stock front bumper air dam, than with the
stock air dam in place. Other 2500/3500 Diesel Ram owners have reported
better MPG after taking off their air dam on the TDR website - but those tests
did not seem to be carefully done.

Weight reduction is supposed to improve MPG - the rule of thumb is " a 10%
reduction in weight yields a 6% improvement in MPG." So 540 lbs off a 5400 lb
Ram might increase 14 MPG to 14.8 mpg.

The US Army is giving some of your tax dollars to Ford as a Research grant to
try out ways to cut the weight of a pickup truck by 25%.

Aluminum wheels save 40 lbs total. New Aluminum Magnum heads save 46 lbs.
Aluminum diff and rear axles saves 150 lbs. Fiberglass leaf springs save 75
lbs or monoleaf steel springs save 40 lbs.

Do Google searches for 'monoleaf spring' or 'fiberglass spring' to find
{direct specific webpages have changed from}

Do you really need that rear bumper - are damaged bumpers less expensive to
replace than damaged sheet metal?

Mopar Perf has a $3000 aluminum 'R' engine block with 9.56 deck height that is
a direct swap for the cast iron Magnum block. If you start looking at the
prices of all these lightweight parts the cost adds up sky high - the mpg
saving would never pay for them.

It is possible that 'Rhoads' style variable hydraulic lifters installed on a
Magnum engine would increase MPG by opening the exhaust valve later and nearer
bottom dead center and closing the intake valve sooner. A 'RV' grind camshaft
does this too. This gets the last little bit of energy out of the combustion
pressure, but it also hurts higher rpm horsepower.

Higher compression ratio pistons are a reliable way to get better MPG.
Usually this means you have to purchase more expensive higher octane gasoline.
Raising the compression ratio from 9 to 9.5 is estimated to give 1% better
MPG. On a Magnum 5.9V8, changing the stock head gasket thickness of 0.047
inches to a Cometic 0.025 gasket will raise the compression ratio from 8.9 to
9.3. Replacing the stock 5.9V8 pistons (with their -13 cc depressions in the
crowns) with flat top pistons of compression height 1.626 inches will raise
the compression ratio from 8.9 to 10.2 Using flat top 1.67 inch compression
height pistons will raise the compression ratio from 8.9 to 11.3

There are combustion chamber designs that claim to allow compression ratios of

10-14 on 87 octane gasoline. You can read about them at:

The last MPG technique is the simplest, but the one few of us want to hear. I
have done several 300-400 mile test runs at steady 60 or 70 mph on I95.
Slowing down from 70 to 60 mph saved 3-4 mpg each time. I also did a 80 mph
test run once driving with the crazy flow of traffic from north of West Palm
Beach to Ft Lauderdale. This lowered MPG by 4 compared to going 70 mph.

Notice that I don't claim this slowing down is 'cheap' because of the
'How much is your time worth ?'

If you want to read more about MPG improvements that work, the US government
has put a book online at:

In the Appendix of this book is an interesting table where the Dept of Energy
sent a questionaire to all the auto makers and asked them what various mods
were worth to improving MPG.

Kevin Gertgen's Fuel Economy Calculator software is very impressive and can be
read about at:

There is an online Java based webpage calculator at:

Jeffery Diamond's Mopar specific gas mileage mod table is worth pondering:
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