....is there ways to get it to get better gas mileage? I think that my 81 full size 2wd 1/2 ton with 318/OD833 gets better.

Trade it in.

I have found that old school V6's give you V8 mileage and 4 banger performance if you are lucky, lol.

Seriously, standard stuff, free flow exhaust, free flow air intake, good plugs, wires, cap/rotor, etc, are about it. There might be a computer "chip" that helps, but I know nothing about that. You might find that a turbo or supercharger would inprove your mileage, but I dunno.

nope. the 3.9L engine was good for um...nothing. as said, abysmal performance, power of a hopped up 4 cylinder, with the gas mileage of a larger V8.


make the truck lighter, swap the gear ratios around, maybe try a custom tune on the engine computer? I think the factory tune was pig rich on these things so that there was lots of gas to give the cat converters something to "chew on" and make them more efficient at their job. dunno if that's true or not though

what year Dakota? My 95 5.2 3.92 sport 5 speed got better mpg than my buddy's 94 v6 3.55 5 speed. Plus it was wayyyyy faster

My 2000 dak ex cab 4x4 3.9 with a topper is getting 3 mpg more than my 2000 durango with a 5.9

I had always heard the 3.9 was just as bad as the V8 but in this case it is not even close, I am happy with my truck, but like my title implys I am in the search for more. Today I put a cold air intake on it, I don't think it will help because the O2 sensor is going to make it dump more fuel in to make up for the extra air. One of thease days I will swap the O2 sensors so the primary one is reading the mix after the cat, that should fool it into thinking it is rich and lean it out a tad, I did this on a 5.2 ram truck and it worked great, the fuel trim went from adding 3% more fuel to takeing away 3% from the fuel map and gave me a consistant 1mpg. If your truck has the 518 trans the A-500 can help because it soaks up less of you already low HP and it can give you some more gear multiplication in 1st and 2nd gear. Another small gain can come from the 8.25 rear, it soaks up a little less power than the 9.25 that a lot of them came with. I pulled the belt driven fans off both rigs and that helps, both of my rigs have electric fans but I have pulled them from my 91 dak and it was fine with no fan unless I sat a long time in traffic, same with my 68 cuda but I have an electric fan on it to turn on in traffic.

I am trying to find info about a computer also so if anyone knows of one I want to know also.

search on the net for dakota web sites. You can put a v-8 throttle body ( not the right term ) and install a 180 thermistat. They also say that you can adjust the tps so you can get more performance.

My parents had a 96 dak 3.9L auto 2wd single cab regular box. Got the same mileage as a comparable 5.2 dak but without the power. They now have a 92 350 chevy pickup that gets basically the same mileage.

Depends on the year and type of dak, but as stated, they generally are not big on mpg. Had a 93 reg cab 4x4 5 speed sport that got 21 strictly hwy.

There are places that do PCM flashes for company fleets to improve gas mileage by altering the fuel/timing etc.

I believe BG chrysler is one of them.

FWIW wife's auto. 02 quad cab gets 17-18. Performance sucks. It won't climb a hill on cruise without kickdown. My '93 club cab 5 Spd. got 18-24 and ran quite well, never needed to downshift for a hill on cruise or any other time. It was the main reason we bought the '02. Wife had to have auto trans. If you're underpowered the last thing you need is a trans that sucks power.

If the truck is an automatic, forget about trying to get better mileage.

The180 t-stat will hurt MPG as the computer will dump more fuel since the CTS says the engine is not warmed up. Altering the TPS will not do anything because it zeros at whatever it was at when the engine is started. The V8 throttle body will not help bcause the O2 sensor will reset the map when it sees the extra air to keep the A/F ratiothe same. The bigger TB will allow you to make a tad more HP at WOT bcause the injector pulse is not going off the O2 at WOT, it will have a fixed injector pulse so it wll lean it out by letting in more air.

i have an 03 dakota/3.9/5speed/ex. cab/4x4 i was getting 17.5 mpg after checking for about 5 tanks fulls. i replaced the paper filter with a k&n and picked up 1 mpg. i know its not much but every little bit helps. getting some taller/narrower tires will help too.

ive been driving a 2wd 3.9 v6 dakota since 95 ,tho the truck is a 92,it has a 3.92 rear axle,and gets better mileage than a similar dakota with a 3.55,3.9 v6,the problem is with the 3.55 rear its always downshifting on even the smallest hill on the road,while the 3.92 rarely downshifts,i have towed some really heavy loads with the 3.92 3.9 v6,and while its a little like the tail waggin the dog,it does do the job,i recently bought a 4x4 3.9 v6 with 3.55 axles,and im gonna change axles in it SOON, both have A500 trannys in them

In these newer trucks and changing gears....does the trans still have the gear cog in the rear of the trans that can easily be changed out to help your speed-o-meter?

Thanks for everybody's feed back.

It may be in axle housing so you won't have to change it.

until 96 they had the gear in the tailhousing like a 904 - 727 but in 96 they got an electronic speed sensor in the tail housing for the govenor and a speed sensor in/on the diff that reads the axle speed and gives you your MPH so if your truck is 96 or newer you can change gears and your computer will never be the wiser

I wish you were closer with those 3.55 gears I would swap them for my 3.92s

a 2003 Dakota SHOULD have the 3.7L v6, same engine family as the 4.7L they dumped the 3.9/5.2 in 01 I think it was? but kept the 5.9L in the R/Ts through 03, I don't think there were any 04 R/Ts

I think instead of TSP--Throttle position sensor, you meant CPS--crankshaft position sensor. the TPS resets every time the truck is started. the CPS is what the computer sets the timing off of. before I knew a lot about these trucks, I thought I'd fill the tank up with premium, and twist my distributor to get more timing and more power.

with the timing light on it and I was ready to go, twisted the dizzy, saw the timing advance, and about 3 seconds later, it went right back to where it was before!

but if you move the CPS, you can gain timing through the entire RPM range and the computer doesn't realize what's happened.

Yes you can slot the CKS and get a couple degrees more timing but not much. Turning the distributer only changes the injector timing and has nothing to do with the ign timing. The only thing about turning the distributer is the rotor and cap terminal may not line up properly when the coil fires.

It's a 2002 SXT club cab 2wd with an 8 1/4 or 8 3/8 I guess now.....with the 500 style trans.

One more question....does the 3.9's idle rough. I test drove two and counting the one I bought and I think that they idle rough. They both ran down the road alright and was smooth, but seem to idle rough.

Is this nature of them or?

The one my parents had idled smooth. Maybe not as buttery smooth as some but definitely not rough.

Most of them do tend to idle rough, one cylinder being a touch off has a bigger effect on the whole when it is one out of 6 than 1 out of 8. Also the chains stretch and the plastic gear wears a lot and that retards the valve timing causing low vaccume and rough idle. A nice tight chain should also help the MPG by closeing the intake valve earlier(actually where it is intended to close) and helping to build cyl preasure, it will also let the MAP sensor know there is not as much load on the engine as it thinks there is based on a weak vaccume signal, if vaccume is weak it thinks there is more load and dumps more fuel.

It's never gonna idle as smooth as a 60 degree v-6, but they seem to be rpm sensitive as far as smoothness goes. Those chains usually can be heard rattling at idle when they're getting too loose.

I've owned a '95 3.9, A-500, 3.23 reg cab and a '01 3.9, 5 speed, 3.55 ext cab and they were both consistent 20 mpg trucks (50/50 city/hwy driving), as opposed to my '97 5.2, A-500, 3.92 reg cab at 14-15 mpg. I towed my Spirit on an open trailer the 80+ miles to Norwalk several times with the '01 with no problems - it wasn't a Cummins, but it had decent power. Odd thing about the '01 - it got poor mileage and had no power till it hit 500 miles, then it was like you flipped a switch; I got noticeably better mileage and power, as if it had a "valet mode" in the computer so you couldn't abuse it until it hit a certain mileage and was broken in.

I think that I'm getting around 14 if I'm lucky with it right now. I've also noticed that goes into overdrive at 30 is this normal?