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180 degree thermostat?


Old 05-05-2006, 11:38 AM
hilliad is offline
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Default 180 degree thermostat?

Does anyone know what is the stock thermostat that comes on the Ram? And what are the advantages of installing a 180?
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Old 05-05-2006, 12:10 PM
Dodgeguy4x4 is offline
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Posts: 25
Default RE: 180 degree thermostat?

The stock thermostat is a 195. The two advantages I see out of it are increased power and a cooler running engine.
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Old 05-05-2006, 12:32 PM
shott8283 is offline
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Location: Bett-neee
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Default RE: 180 degree thermostat?

180 tstat will keep the actuall engine cooler, helps to resist engine ping, sparknock, detonation etc. Also it will help to keep the intake charge cooler, providing a wee bit more power too. Although that last statement is something to be debated about over and over. A cooler engine is a happy engine. A cooler engine is a longer lasting engine aswell. Brands to stay away from, pretty much hypertech, their tstat kinda blows. Napa is a good brand.
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Old 05-05-2006, 12:46 PM
HankL is offline
Join Date: Aug 2005
Posts: 3,313
Default RE: 180 degree thermostat?

Coolant temperatures and thermostat settings

There is controversy about MPG and thermostat temperatures but there
seems to be a clear trend that higher coolant temperatures controlled by
195-203 setting thermostats improve MPG slightly.

Sadie Carnot's 200 year old thermodynamic theory says
that cooler air intake temperatures would give improved fuel economy
because cooler air takes slightly less work to compress, and if a
140-180 thermostat is used on an old fashioned iron or aluminum
intake manifold with coolant cross-over passages there will
be less temperature rise in the intake air as it passes through.

Modern intake manifolds such as the ones on the 4.7V8 and 5.7 Hemi
are made of insulating Nylon66 plastic so this does not
apply as much - although the incoming air can still pick up
heat from the metal walls of the cylinder head ports.

But hotter oil on cylinder walls has less viscosity and creates less
friction against the piston rings - which can also mean better MPG. The
Cummins 'Secrets of Better Fuel Economy' white paper listed at the top has a
graph showing this on page 12. Theory also predicts that hotter block walls
and cylinder heads will absorb less heat from combustion and permit a greater
pressure 'push' on the piston.

The new four cylinder 'World Engine' in the 2006 Dodge Caliber has two
thermostats: one to feed lots of cooler coolant flow to the cylinder heads
so that pinging will be reduced and an MPG improving higher compression
ratio can be used - but another separate thermostat setting to adjust the flow
to the engine block walls so that they stay hotter and ring friction will be
lower. This may be the best of both needs.

Some Dakota owners who switched to 180 degree thermostats have reported less
ping, peppier acceleration and about +1 mpg, although most reports like this
are just about what their next tank of gasoline yielded - not a careful test
that you can trust. Other Dakota owners reported no mpg change or a loss.
Four Wheeler magazine reported +0.8 mpg gain with a 192 to 180 deg
thermostat swap in a 454 Suburban. Take these reports with a grain of salt
considering who did them and how magazines live on advertising.

My own experiments with a failed thermostat that cracked and stayed open at
around 140 degrees, then later thermostats of 180, 195 (stock) & 205 showed
no significant improvement in MPG at steady 60 mph highway cruise
on a 1995 5.9V8 Ram CCab shortbed, although the 205 did measure a
0.2 MPG gain in one 300 mile test run.

The 180 degree thermostat also did not reducing pinging at least 'by ear',
nor did the 205 thermostat increase pinging by ear, but a better test would
have been to measure with a MSD aftermarket knock sensor, or better yet
read the memory of a J&S aftermarket anti-knock ignition system with its
twin knock sensors and better knock detecting software & chip.

Why would this be if you have read a thousand internet postings that
180 degree thermostats reduce detonation? This may be because the
Dodge PCM computer senses coolant temperature and either
advances or retards ignition timing as necessary according to the
tables in the memory of the computer's software. The cracked
thermostat that stayed open at about 140 did reduce pinging by ear.
When you read that 180 degree thermostats reduced pinging on old
carburetor engines that might be true, but consider that today's
computer controlled engines 'have a mind of their own'
inside the PCM that carb'ed engines did not.

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.

Respected tech editor Marlan Davis of Hot Rod magazine has reported that
all things considered, fuel economy is better with coolant at 210 degrees F.
Perhaps that is why the factory thermostat on the 5.7 Hemi is now marked 203
F, which is were it begins opening. 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. This would lead one to
guess that the coolant coming out of a 5.7 Hemi is hotter still. The 5.7V8
now also has a closing bypass post sticking out from it that closes off the
bypass passage and results in greater coolant flow to the radiator once the
engine is up to designed temperature. This allows the water pump to be run
slightly lower in rpm and saves a bit of fuel.

Someone who is up to doing experiments could remove their thermostat entirely
and cut/weld in an electrically controlled valve in the tall metal nipple
above the thermostat flange. With this electric valve and a temperature
(there are several adjustable ones for on sale for electric fan control)
you could then have an adjustable thermostat.

For much cheaper & simpler you could also just put in a cable operated valve
and keep a 180 thermostat in the housing. Another option would be to
install a set of shutters to restrict air flow through the radiator to bring
up coolant temperature. Either of these would allow you to raise the coolant
temperature while at steady highway cruise to something like 220 with
50/50 conventional coolant mix (or 260-300 with Evans NPG coolant)
which might improve highway MPG by maybe 0.2-0.4

Coolant temperatures also affect bore wall wear, according to experiments
run by aircraft engine manufacturer Continental Engines in the 1960s.
Bore wear is relatively high at 140-160 degrees but begins rapidly leveling
off at 180 and shows no improvement above 205. It is thought that this wear
effect is due to acidic liquids condensing on the metal bore walls and
corroding them. Above a certain coolant temperature the liquids never
condense and remain gases. A similar problem happens in the chimneys
of power plants.

Cylinder Balancing

Each of the cylinders in a Ram pickup engine is a little different than its
neighbor cylinders due to 'production tolerance' at the factory. In the 2003
official Ram Field Service Manual (FSM) specifications for the 5.7 Hemi
the table has a line saying the variation between cylinders can be 25%
and still be acceptable to DaimlerChrysler. Each cylinder's fuel injector
sprays slight different amounts of fuel per second, and each cylinder has
a slightly different airflow through its intake runner, cylinder head port
and valve. If you are lucky, just by chance your engine will have its
highest flowing fuel injectors installed in the cylinders that also have the
highest flowing airflow. If you are unlucky, your 'lemon' engine has the
lowest flowing fuel injectors installed in the cylinders with the highest
airflows, and vice versa.

The amount of air mixed with fuel is called the 'air to fuel ratio' (AFR) and
for decades racers and engineers have known that this AFR ratio affects
fuel economy, torque, and the temperature of the exhaust gas coming out
of the cylinder. Also for decades, people have tried to 'tune' the AFR by
measuring the temperature of the exhaust gas. The best setups for this are
expensive, but you can buy much less expensive instruments today. Sears
has multimeters like this one with a retail price of $40 but is sometimes on
sale for $20:


that has a Type K thermocouple that will measure from 0F to 1400F if you are
careful not to burn the insulation, which is only rated to 550F. By drilling a
in your exhaust manifold at the 'traditional' distance of 1 inch out from the
exhaust port and inserting this thermocouple you can measure your
exhaust gas temperature (EGT) and then swap around fuel injectors to the
cylinders where the combinations yield nearly equal EGT for all cylinders.
By equalizing your EGT you can improve both torque and fuel economy - and an
added bonus is that your engine will be less likely to 'ping' on one cylinder.

How much improvement can you get? It depends on how unlucky your engine
was from the factory, but typical improvements if you can get the cylinders
nearly equal are 6% better fuel economy at part throttle operation during
highway cruise, and 4% better power at wide open throttle too.

Some notes on EGT testing: If you can find the Sears multimeters on sale for
$20 it might be better to buy 4 and test one side of a V8 at the same time,
then later give away the other 3 multimeters as gifts to friends and family.
With the 36 inch long leads from the thermocouple tip to multimeter you
will have limited distance so mount the meter outside your windshield,
at the rear edge of the hood, perhaps mounting 4 meters on the same board.
Choose a hole size to drill that you can later close off with a blind rivet or
tap and close with a stainless steel screw. Buy a $12 'muffler patch' kit
and use the high temperature felt gasket material to place under and over
the thermocouple wires for protection and insulation, then use a large
stainless steel hose clamp to hold the thermocouple in place during testing.
Make each test run on the same stretch of highway at about the same
air temperature with the same gasoline. Measuring EGT at the rpm of
maximum torque at full throttle is the normal spot to record the
temperatures. Testing on a steep hill where rpm changes more slowly
as the truck climbs and you can stay at legal speed is a wise idea.
Have a partner drive while you watch the meters.

You can gain additional information about the air/fuel ratios of the
various cylinders using a $60 'Colortune' sparkplug:



One note on the limitations of EGT testing - your engine's cylinders
also vary in their true 'dynamic' compression ratio due to sloppy
factory tolerances. Cylinders with higher compression ratios will
have LOWER EGT readings even if the AFR is the same. You can get
hints about what cylinders have higher dynamic compression ratio by
doing a compression test on all cylinders before EGT testing. The
best way of balancing AFR on cylinders is to use a 'wide range' O2
sensor in each cylinder's exhaust. This has been very expensive in
the past but the cost of wide range O2 instruments has been coming
down. See these two links:



Valve Timing & MPG

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. One Ram owner with a
heavily modified 406 stroker Magnum V8 measured a 3 MPG gain when Rhoads
lifters were installed, but his camshaft was pretty 'wild' to the point that
he only had 7 inches vacuum at idle originally and that improved to 11 inches
of vacuum after the Rhoads lifters were fitted.


A 'RV' grind camshaft with lesser duration does this too.
Lesser duration on the exhaust valve cam lobe usually closes
the valve later toward bottom dead center and gets the last little bit
of energy out of the combustion pressure, increases 1500-2500 torque,
but it also hurts higher rpm WOT horsepower when large amounts of
exhaust gas is trying to escape the cylinder and now has to start

Jim McFarland is an advocate of modifying piston tops. His design for the 4.00
inch Chevy 350 piston could easily be applied on flat top Magnum 5.2 pistons:

The 'soapdish' piston top on Magnum 5.9V8s might need some modification but
the 3 sets of dimples might still go in the same general areas. McFarland
claims 2-5% gains from this piston top modification. More info at:


Special ceramic coatings on the crowns of pistons and on the combustion
chamber of the cylinder head can improve both fuel economy and torque by
holding heat inside where it can produce pressure on the piston. Racing
engine builder Joe Sherman states that these coatings can add 2-3% to
performance, but if professionally applied they can be so expensive that the
mod would not pay for itself in fuel savings. There is an article about
applying coatings yourself at:


Honda claims that one of the tricks used in the Insight 3 cylinder engine to
reduce friction is shot peening of the piston's outer diameter. Quote:
"LOW-FRICTION PISTONS In the interest of friction reduction, Honda
engineers specified a new lightweight aluminum-alloy piston design
for the IMA engine. The pistons have a minimal skirt area and the surface
of the skirt has been shot-peened. Shot-peening is a process in which a
metal part, such as a piston or connecting rod, is blasted with shot-like
particles, creating uniform, microscopic dimples on the surface. This
dimpled surface is better able to retain a lubricating oil film. Shot-peening
the IMA engine's pistons accounts for another 1.5- to 2.0-percent
reduction in internal friction."
There are further descriptions of friction reduction techniques used in this
engine, including offset bores for less side load from the con rod, at:


Compression Ratio
It is a shame that the term 'compression ratio' became the standard term used
to describe this important part of engine operation. It is much more valuable
to refer to this as 'expansion ratio.' Once you begin thinking 'expansion
it becomes common sense as to how to get better fuel economy in an engine:
you want to first generate high pressures in the combustion chamber from the
burning of the fuel and air when the piston is at the top (so keep the
open) and then you want to expand it as many times as possible to get the last
little bit of push on the piston as it makes its way to near the bottom.
with compression ratios of 9 expand the gases a little less than 9 times
{a little less because the exhaust valve opens before the piston gets to the
Engines with compression ratios of 12 expand the gases more and get a last
"bite of the apple" for a small increase in both fuel economy and power.
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

This webpage has hard to find details about compression ratio increases from
milling cylinder heads of various sizes and makes.

Fitting 6.1 Hemi cylinder heads on a 5.7 Hemi should boost the compression
ratio by about 1 point, and the sodium filled exhaust valve on the 6.1 cyl
head would also help control pinging and detonation with this higher ratio.

There are combustion chamber designs that claim to allow compression ratios of
12 to 14 on 87 octane gasoline. You can read about them at:


The USA Environmental Protection Agency has published an interesting paper
on converting a VW TDI diesel engine to sparkplugs so that it can run on
either of the alcohols methanol or ethanol, which have high octane ratings in
the 105 to 109 MON range. This engine runs at a compression ratio of 19.5
and avoids using a throttle (except at idle) by using a turbocharger with
high exhaust gas recirculation.


EPA reports that earlier research showed that increasing the compression ratio
from 8 to 18 improved fuel economy by 16%.

This EPA paper also reports that they tested many port fuel injectors and
found that the 12 hole injectors sold by Holley Inc. gave the best spray
pattern and smallest and most uniform droplets.

The paper is full of 'Geek Speek'
but is worth reading a few times if you are interested in engines.
Note their 'load maps' and how they refer to the area of best fuel economy
as an 'island' that sticks up out of lesser fuel economy areas. The
EPA paper is jammed full of information but it is a shame that they didn't
also make runs with this engine on pure chemical Octane with its
100 rating, which probably would have worked too. The use of the pure
chemical Octane to test engines is traditional as a way to make sure engine
testers are comparing 'apples to apples' when exactly the same gasoline is
not available everywhere.

Sparkplug and ignition advance changes.

I did a careful test run of 311 miles after indexing sparkplugs in a 5.9V8 and
measured what might have been a 4% improvement. That could be random
variation. 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.

There is an article with several good illustrations of sparkplug indexing at
this Ford site:


On a 5.7Hemi, it is very probable that by re-arranging the stock 16 plugs to
their best position in the cylinder that is 'lucky for them', you could
achieve indexing without buying more than 4-6 additional plugs at most,
perhaps none at all. Aim the open gap toward the exhaust valve.

Tests of the Bosch+4 sparkplugs at 60 and 70 mph highway speeds with 87 octane
gasoline found no MPG 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. Consumers Reports found similar results when trying
Bosch+4 sparkplugs on a Honda.

Exhaust Gas Recirculation and MPG

1992-1995 Dodge Magnum 3.9/5.2/5.9 engines had exhaust gas
recirculation valves. Then from 1996-2003 EGR was dropped, probably
because the 3-way catalytic converters got more efficient at removing
NOx gases from the exhaust. In 2003 the 5.7 Hemi V8 showed up
and it had EGR again along with dual sparkplugs that might be there
to make the EGR work better (they help low RPM torque too).

Legendary MIT professor and former racer John Heywood wrote the
most used college textbook on engines:


on page 837 of Heywood's book he has a graph that shows that if you have
an engine with the right cylinder head design (closed chamber & fast burn)
and highly dependable ignition (like dual sparkplugs),
up to 25% EGR flow can improve fuel consumption when the engine is being
run at part throttle like a Dodge Ram pickup would be at highway cruise.

GM's Opel division also thinks EGR can increase MPG about 6%:


If you are a tinker and have a Ram in the 96-02 gap where EGR is not
used you might consider rigging up a line with a remote control valve
from the exhaust to the air cleaner inlet. Make sure your ignition system
and sparkplugs are in tip top shape because too much EGR flow can also
cause missfires - which kill any MPG gain if they begin occurring.


In the Cummins White Paper they cite a study where there was a 30% variation
in MPG between professional drivers in the exact same truck over the same
route. This is similar to GM research, such as this from from page A3 of The
Wall St Journal on 11-21-2005:
"Roger Clark, GM's senior manager of energy and drive quality in North
America, said the current test does a good job measuring average mileage but
the problem is the variation in how people drive. He cited a GM Study of 209
people driving the same midsize SUV. The fuel economy varied from about 13
miles per gallon to 23 miles per gallon, depending on the driver."

There are 'experts' at driving to get the best MPG. You can read about
John and Helen Taylor, a husband & wife couple who are sponsored by
Shell and have won many contests at this link:


Note the list of good driving techniques for better MPG near the end of the
article about the Taylors.

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
question: 'How much is your time worth ?'

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Old 05-05-2006, 12:57 PM
shott8283 is offline
Join Date: May 2004
Location: Bett-neee
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Default RE: 180 degree thermostat?

Yea, what HankL said.

Sometimes I wonder if Hank is a real person, sometimes when I read his posts, I think to myself that he must be some artificial Dodge inteligence. lol
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Old 05-05-2006, 01:01 PM
TPSDODGE is offline
Join Date: Jan 2005
Posts: 225
Default RE: 180 degree thermostat?

hankl....you just made the longest post in the history of the internet..but i always feel enlightend after reading, so thanks for the info
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Old 05-05-2006, 02:50 PM
muddy_blue_dodge is offline
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Join Date: Feb 2006
Posts: 1,656
Default RE: 180 degree thermostat?

its one of those things where you start reading it at the top, then scroll down a little, and a little more, and a little more, then you realize how long it is and you end up just skimming it


but great info, thanx
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Old 05-05-2006, 04:11 PM
crazy1snow is offline
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Join Date: Jul 2005
Location: White Salmon Wa
Posts: 1,015
Default RE: 180 degree thermostat?

ow... i read enough textbooks...

good points though. i wonder if the .2 mpg is worth having a higher temp thermostat or a lower one... .2 mpg.. yeah it's worth having the 195 yet...
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Old 05-05-2006, 04:18 PM
Silver_Dodge's Avatar
Silver_Dodge is offline
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Default RE: 180 degree thermostat?

I think you would have to be in a very controlled environemnt (like a test lab environement) to even truely be able to know that you are getting .2 mpg increase or decrease. In regular everyday driving, mileage can fluctuate more then .2 just by how many stop lights you hit on a tank of gas, or how much highway miles you drive, etc...
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Old 05-05-2006, 05:00 PM
Socha_62 is offline
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Location: Gaylord, MI
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Default RE: 180 degree thermostat?

Hank, I've seen you post that like 10 times.

Needless to say I've never read it all lol

I just threw a 180* Stant thermo in yesterday when I did my plenum for ****s and giggles.
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