If you look at a "completely stock" 5.7 Hemi 4x4
a 3.55 differential in 0.67 top gears puts the
best engine fuel efficiency in terms of converting
a pound of fuel into hours of horsepower
right near 65 mph.

In a similar way
a 3.73 differential puts the optimum
right near 77 mph.

If you think about those numbers
that is exactly what you expect a Dodge engineer to do
for the 'average customer'.

You can also work out where the best engine efficiency
is for towing a 5000 pound trailer in 1.00 third gear
and you get around 60 mph - which also makes sense.

If a Ram owner 'improves' his truck by adding a tonneau for aero improvement
of low rolling resistance tires, or swapping in an electric fan,
then he could drop to a numerically lower gear ratio.

If a Ram owner puts an added 'strain' on the truck by putting on wide aggressive tread 'mudder' tires that roll with more resistance, or adds a 'bug deflector' or light bar that has wind drag then he would need a numerically higher gear ratio.

I read many posts from fuzzy thinkers who say things like:
"It's a truck so you shouldn't even care about MPG"

I am thankful those people don't handle my checking account.

It is the vehicles that use a lot of fuel
- trucks, airplanes, boats
that can save the most money from small changes in efficiency.

Walmart has recently announced
that the best way to improve profits
is to change its trucks so that they go
from just below 7 MPG (already good by 18 wheeler standards)
to 12 MPG.
That is going to be a tough job but Walmart says they are willing to spend a lot of money on Research and Development to make it happen.

 

"I read many posts from fuzzy thinkers who say things like:
"It's a truck so you shouldn't even care about MPG"

I am thankful those people don't handle my checking account. "

Hank, Hank, Hank . . . . is a "fuzzy thinker" someone who buys a 5,500 lb truck with 345 hp and wonders why he gets 12 mpg? Or is it someone who says that is to be expected with that sort of weight and hp? I think the answer is clear.

Secondly, if someone thinks getting .7569058403 mpg better is going to improve their financial standing, then they are the most ignorant money managers of all. For who buys a $25,000+ truck, that weighs 5500 lbs, that gets 345 hp at the crank, has a larger than most monthly payment, pays a higher premium in auto insurance when they could have purchased an $11,000 economy car that got 35 mpg? Again, the answer is clear, for the reasons I mentioned - the truck has more initial cost, higher taxes on the purchase, larger monthly payment, higher insurance premium, higher maintenance cost, higher registration, and higher fuel costs when compared to something truly economical.

We buy these trucks for several reasons - either because our jobs demand it, or we want the power and enjoyment of it. Again, I know some people buy big trucks with large motors to haul the kids. If you have the money, great. But if you think it will be economical - and save you money in the long run - you are kidding yourself.

I would say the greatest way to improve gas economy is to park the truck in the driveway and get a 4 banger that gets 35 mpg. Because all this crap about cruising under 1900 rpm's, coasting, driving with the wind instead of against it lol, and such is a minute detail in the large picture. Bottom line, hauling around that much weight is going to kill your gas mileage. And, if someone wants to sacrifice the enjoyment of the truck for $2 savings per tank, that is their choice. But, I'd rather get my enjoyment out of it (having a lead foot when I want to) and pay an extra $2 a tank.

 

LOL - Exactly! Bought the truck new and drive on weekends or when the situation demands. Paid $1850 for a 95 Geo Prizm (same as the Toyota Corolla, BTW) that gets nearly 40 mpg and requires almost NO maintainence other than basic fluid changes. In 6-7 months with my wife driving about 600 miles a week, it has already paid for itself in fuel savings, insurance savings and keeping the miles off the new truck plus if someone opens a door into it or pushes a buggy into it, I don't care as much.
You want to know the best way to increase your fuel mileage? Read my first paragraph. You can spend $1500 in mods that will net you another 2 mpg or just buy a $1500 Jap beater and stop whining!

 

I agree with many of AIR RAM's suggesetions. I noticed a 1-2 increase by installing my CAI and driving easy, as I usually do on the highway with the truck (in a car its a different story, lol). I plan to install an underdrive pulley, and electric fan this summer as well. I'm looking into the 4.56's but only because I plan to run 35's which won't help fuel econ. at all.

P.S. Damn Hank, who is gonna spend all day and read all of that?! hahaha.

 

I've seen some great replies on here. Never the less, I don't think our topper helps. If y'all watch mythbusters, it shows a spin in the bed happens causin' air to flow over the tailgate. But 10mpg isn't the greatest, but sounds right.

-BigRig

 

How to do a MPG test you can depend on
----
Got a buddy with a Dodge Ram with the overhead trip computer?

Since you are making a modification with hopes of getting better MPG
why not do a "before & after" test?

* you and your buddy fill up at the same gas station and put the same air
pressure in all tires
* Pick a highway without too much traffic and hopefully where the wind is a
head wind or tailwind (side winds mess things up)
* Your Ram and your buddy's Ram follow one another staying at least 6 vehicle
lengths
apart.
* talk to one another with cell phones or walkie talkies
* drive at the same speed
* reset the overhead computers at the same time
* drive at least long enough to burn up one gallon
* write down average MPG at end of run
* exit highway, turn around, and do same test again in opposite direction
(this is to cancel out wind direction)

After doing your modification redo the test,
hopefully at a time of day where the temperature is about the same as the
'before' test.

The value of your buddy's Ram is that on this 'after' run if his MPG is
greatly different you should suspect has gone wrong - like strong cross winds
or a change in temperature, tire air pressure, etc

If you want to test two trucks against one another
that are already modified
like comparing 3.55 differential gears to 4.56 gears
(or an underdrive pulley, thermostat, SuperChips, etc)
you can modify this test slightly.
Swap two tires from one truck to the other.
Now both trucks have the same 'average' tires.
Weigh the trucks and add weight to the lighter truck to make them even.

If you really want 'gold standard' accuracy that you can REALLY trust
(or if you are measuring a small effect like a thermostat or synthetic oil)
then swap the mod over to your buddy's truck
and do the tests another time with your truck as the 'control'.

By doing a test this way you are doing a simplified version of a SAE/TMC Type
IV fuel economy test RP 1109. Here the SAE stands for Society of Automotive
Engineers and TMC stands for Truck Maintenance Council which is a group
of professional 18 wheel truckers who have banded together to share
information.

Credit for inventing a 'good' MPG test like this goes to many, but
especially Claude Travis, known to his peers at TMC as "Mr. MPG,"
has spent 37 years managing the operation, maintenance and testing
of heavy-duty, on-highway vehicles. Highly regarded for his exhaustive
research in the field of heavy-vehicle fuel-economy, he is principal of
Claude Travis and Associates, Fleet Consultants, Grand Rapids, Mich.

http://www.etrucker.com/apps/news/article.asp?id=22903

 

I'm not sure that I agree totally with the above quote because when I open the tailgate on a 300 mile(one-way) trip I take quite frequently, I save full 1/4 of a tank on my 97 Ram 1500 5.9 4x4 Auto/Overdrivewith the tailgate down.

I also try to keep the RPM's to under 2000 if I can also helps quite a bit. Yes, it takes alot longer to get to cruising speed but I usually ain't in that big of a hurry.

 

I know a way to get one hundred miles to a gallon on a Hemi. and it's no April fools Day joke. Go to this web site. www.lpga.couk/lpga.htm Now I know this works. A lot of City buses are now using this method. an our government is paying for it. and in Canada if you have it put on your truck the pay you back $2,000 . The only problem is who has it here in the US. And why doesn't GB want us to use it. ? What you do is after you start your engine on gasoline ,when you get upp to speed ,you switch over to propane ,It's that simple. 300,000 miles on a set of plugs. oil changes at 50,000 miles.The engine will almost last for ever. I used to work for a major oil refiner We had a car that ran from Ny City to California on a tank of gasoline It was a four cyclinder engine with this set up. If anyone finds out the place that sells it here in the US please post so we all can get in on the savings. Good Luck.

 

I have driven 4 wheel drives all my life. And they all get poor gas mileage. The Mitsubishi Montero I owned only got a couple of mpg better than the Ram. I owned an Isuzu Trooper before that and I think it averaged around 18-19mpg..and that's with a 4 cylinder engine. It's the sacrifice we make for driving what we love to drive. If I were going to be obsessed with gas economy....I'd buy a hybrid and get 50 mpg. But right now....I say fill er up once or twice a week and floor it every chance you get. This is the greatest truck on the market. Enjoy it.

 

According to the Mythbusters and other independent studies, driving with the tailgate down or off decreased mileage!?
Mike
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