Those things mentioned above are really the best ways, especially that first one. Plus, I believe someone mentioned getting better tires. Highway tires will roll easier, and give you better MPG. A/T tires or off-road tires will of course be more designed for traction and give you worse MPG.

I have the 5.9, CAI, high flow cat, and performance exhaust. However, I have A/T tires (bigger than stock also) and a lead foot. My MPG in the city usually hovers around 10 MPG when its cold out (I've seen it range from 9 MPG to 11 MPG) and I'm usually around 12-13MPG on the highway. Again, this is when its cold. I haven't owned the truck through a summer yet, so those are probably the worse I'll see.

When I originally bought my 1995 Dakota with the 5.2 many years ago, it had cheapo highway tires on it. I got a consistant 17.5 to 18.5 MPG on highway, depending on if I had the A/C on or not. In town, I'd get 13 to 15. Subtract 1 or 2 MPG off those for winter numbers. However, then I put 30x9.5 A/T tires on it (by no means huge, but bigger than stock), and my mileage on the highway dropped to 15ish and in town to 12-13, during the summer.

Your tires and your driving habits are the two things that usually affect MPG the most in our Rams.

 

throttle body spacer nope;direct injection is what we got so wont do athing dont even no why they make it.use good maintiance plugs wire and all that good stuff highway tires michalin will role the best for the longest.also a good wax to make it slip threw the air and if that dont work use ky jelly.do not take off tail gate u get better mileage with it on see mithbusters it pruff.

 

Alot of the warm-up period has to do with the o2 sensor warming up. Until it warms, the pcm uses a set of rigid fuel maps that are, in my case anyway, way rich. Since I installed the wideband setup that has a led indicator that lets you know when it is warmed up, I have been turning the key on and waiting until the sensor goes into operation mode then starting the motor. This has eliminated the period of running extremely rich every time I start-up. It kind of sucks on a cold morning because it can take up to a minute, but, after that,re-starting throughout the day can take anywhere from 10-30 secs. depending on how long the truck has been off.

With this setup, you can also program the control unit to output lamda at any a/f ratio you want. Next long drive, I am going to program it for 15-15.3 instead of 14.7:1 and see what that does to mileage.

+1 on the backpressure of your exhaust. Switching from shorties and the stock y into a Magnaflow 2x2.5 out to long tubes into a 3" y into aracing cat into a Flowmaster 40 2x2.5 out netted a solid 1.5 miles to the gallonon the highway.

 

Hooked on phonics................

 

mopar brings up a very worthwhile possibility
that waiting for the 12 volt electric electric heaters built into
the factory O2 sensors to heat up on a cold start
might improve MPG...especially in city driving

it also brings up a 'hacker' idea
very similar to the IAT & resistor mod (aka Powerwire)
that perhaps adding a manual switch and parallel resistor to the coolant temperature thermistor electrical circuit to use temporarily during a cold start
might also slightly improve city driving MPG
by fooling your PCM computer
into thinking your coolant had got up to 147 degrees F sooner.

 

What is the norm for open loop to closed loop transition? I have read lots about how the pcm looks for a certain coolant temp, but my scanner reports closed loop as soon as the o2 sensor warms up.

 

I believe it is around 147 degrees F for both OBD-I and OBD-II

I believe that the DTC code for a 180 thermostat usually reads something like:
'failure to achieve 147 degree coolant temperature in specified time'

my memory is hazy on the subject
but I believe I read somewhere that
the first 60 seconds of 'cold start'
is so hard for the automakers to meet emissions wise
that they found by trial and error
it was better to start super-rich
and avoid any sparkplug misfires due to lean mixture
rather than to have a misfire that then would not be 'cleaned up'
by a non-working catalytic converter still too cold
to reduce the HC and CO gases
passing through it in that first minute of cold engine operation

 

Thanks. Have you run across anything about whether or not a slightly higher a/f ratio would improve mileage? At some point theadded heat and less powerhas to come into play, but I wonder what 15 or 15.1:1 would do.

 

The Performance Trends Fuel Economy Calculator
estimates that going from 14.7 to 16.0
should improve the MPG at a steady 70 mph
from 17.8 to 18.5
at 50 degrees F on a level windless highway
with a stock non-MDS 5.7V8 Ram