80 chrysler lebaron 318 mileage improvement

I have to dispute that going to a numerically higher differential ratio will help city driving MPG.

Where the MPG might be hurt is if you are impatient and put your foot down on the pedal, which triggers both the accelerator pump and takes you into the factory fuel enrichment mixture region.
This can easily hurt city MPG by 30% or more
but is not caused by the differential,
but by the driver.

Keep a light gentle foot and the low numerical ratio with help you.... better MPG was why Chrysler put it there years ago, both for
highway MPG {that requires almost no driver skill}
and for city MPG improvement {that improper driving technique can totally destroy}

For a second opinion ask a 'Hypermiler' that has been competing and has placed in the top 3 of any such event.

If the original lean burn system seems intact, consider buying or borrowing a portable wide range oxygen sensor system
and try to make sure the air to fuel ratio is where Chrysler intended it to be,
along with ignition timing that will seem
'way too advanced'
compared to the numbers you regularly hear.

However, the easiest way to get better city MPG
is to change tires
to one of the
'low rolling resistance' designs.
Here's a link to an (old) listing:

http://ecomodder.com/forum/showthread.ph...report-520.html

There is a also a report from the USA's 'non-partisan'
National Academy of Sciences
about tires that came out a few years ago:

http://www.thefreelibrary.com/Tired+of+rolling+resistrance.-a0145827934

The other reliable way to get better city MPG
is to rebuild the engine with much higher compression ratios.
With very lean air to fuel ratios (18 to 24)
these high compression ratios won't cause knock like you would normally expect
with tunes designed for maximum horsepower.
A city MPG gain of up to 15% is possible.

If you visit a Ford dealer and look into one of the Escape Hybrids, you will find that the compression ratio there is 11.7 on a 4 cyl engine that can use 87 octane.
Google 'Atkinson Cycle' for more info.

It is even more money
but noticeable city MPG gains
can come from choosing a custom
torque converter.

I can post about 40 more pages of stuff if you are interested.

360 veiw is right about the gear ratios. When I set up my mpg car to have very early low speed shifts I got the best in town mpg. If you have a higher gear you will have less manifold vaccume causing pumping loss, and that is one of the things they always bust there buts to eliminate in production cars and is the main thing behind the MDS fuel savine feture so many newer cars are useing.

I think you are doing pretty good already but if you wanted to make it a little better get the 302 heads, they are a cheap and fairly easy up grade. I would keep the lean burn if it is woking good (as it seems to be). While you have the 302 heads off polish the bridge between the valves so they absorb less heat and that will help keep em from cracking and grind down and the sharp point in the center of the chamber because it causes pre ignition. Those heads will help increase low speed velocity and mixture motion both in the port and in the chamber, those two thing s will help mpg as well as the small bump in the compression.

Id live with what you have and wouldn't change anything. There's a lot of people with these cars who don't even get the mileage you're getting. It also depends on what kind of city driving you're doing. When I drive my car to work and nowhere else i get terrible gas mileage but if I still do city driving but actually drive around more it gets better.

Back in the days, "the Cordoba" got 14 mpg with the AC on.

Steelies on pizza cutter tires.

195/80's floated you around.

And it could bearly squeal one tire.

THANKS for your input guys, a little more info on car, LEAN BURN is long gone from previous owner..choke does kick off to idle after start up..and my city driving consists of a 6 mile trip one way back and forth to work(sometimes thermosat does not open till till 2-3 miles into journey) four times a day city driving with stop lights. I drive sensibly and car does not seem to labor taking off from stop lights(does seem to have a flat spot just off idle which I read may be the step rods may need to be raised) which leads to the starting point I may want to take being t/q has 1/16 smaller primarys and a manifold delivering more torque..again thanks for your input..on a last note I've heard 85 and later trucks equipped with rochester spread bore get better mileage than previous years with t/q.

If your commute is only 6 miles long,
consider getting an electric block heater
and an electric timer to turn the power to the heat on about 2 hrs before you drive.

If the troublesome original Chrysler lean burn system
is 'long gone'
and if you are still willing to spend some $ for improved MPG
consider getting a
Chrysler 318 or 360 TBI throttle body & manifold
from a salvage yard
and for control connect it to a moderate cost MegaSquirt ECM
using a wide range oxygen sensor
to correctly control the air to fuel ratio.

My guess is that this type of modernized
'Lean Burn' system
would give about a
4 MPG gain in city driving,
and perhaps more at highway cruise.

In addition
with the flip of a few switches
the settings could be changed inside the MegaSquirt to a maximum horsepower tune
with revised a/f and ignition timing.
Forty to fifty added horsepower might be a ball park guess of the gain of such a tune... even more if this performance tune was for E85 fuel.

If you are getting 17 mpg on a 6 mile commute in the city.

You need to post on what YOU are doing, not asking us!

With number like that. I'm assuming you are already well versed at vacuum advance.

I have a set of small advance springs I want to try but have not gotten around to it..have bumped initial timing 5 degrees over stock till then.

honestly, 17mpg in that commute in an M body is doing pretty good. I can't think of anything cheap to significantly improve this.

if you wanted to spend some coin, maybe try duplicate hotroddave's fuel economy build.....or at the very least, a 4bbl intake with a small q-jet or t-quad might give 1-2mpg better mileage than the carter BBD 2bbl you probably have, as long as you keep out of the secondaries.

A 6 mile commute with those numbers is very good.
It sounds like you are getting about as much as possible now, so improvements from here are going to be tougher.
I'd suggest trying synthetic lubes, an alignment, and decreasing the rolling resistance.
What tires and pressures are you running?

As mentioned, there are engine changes that can help, but at what cost? Raising the compression and installing EFI will cost ten times the 152 buck savings, when you consider tuning, gaskets and fluids and the parts. If you do go inside the engine, I'd also look at coatings.

What engine temps are you seeing? Late model stuff is run very warm. If your cooling system can handle it, running warmer can get more MPG.

Just changed rear end fluid to redline 75-90 synthetic, will have to wait for results. Tires are cheap but narrow tread 205/75/15's with 45PSI front and 40PSI rear

Here's a graph from the internet archive (Wayback Machine) where the U of Florida did an experiment with short city driving style commutes:

http://web.archive.org/web/2006050719451...nce-500x361.jpg

the full archive of the original webpage
which has more advice on improving MPG
is at

http://web.archive.org/web/20060507194510/http://www.fsec.ucf.edu/Pubs/energynotes/en-19.htm

if you have a six mile commute, get a bike