Loss of fuel efficiency

[Chris]

94 Dakota 3.9L 145000+miles
The last fill up 19.756 gallons. I had gotten 286.1 miles out of that which makes for 14.48 MPG, mostly in town on trips no more than 20-25 miles tops with lots of stops.

I had 9MPG when I bought it almost 3 years ago with about 140000 miles.
I started with a new EGR the only code it had, then Plenum kit, Timing chain and tensioner, wires, all new sensors on the intake and TB, plugs, cap, rotor, cam and crank sensor, O2 sensor new serpentine belt, rebuilt Bosch injectors from Motor Man. I got it up to 19+mpgs
I recently fixed exhaust manifold leaks and broken studs and replaced all pipe, Cat & muffler from the Mani back. Did the CAT break in as described in the manufacturers vid.
All of that new stuff is under 2 years old.
I just finished the exhaust a few weeks ago and put on new tires. On a 500 mile Hwy trip I got 19+mpgs and I was heavy on the gas. All driving since that trip has been in town with short trips less than ten miles at hwy speed.

I have read that it matters if you don’t use the exact right brand of wires, plugs, sensors etc. I priced a cam and crank sensor with the dealer and they want north of $120 for one and north of $130 for the other. !!! So that’s a no unless its absolutely necessary.
Any ideas where I should look for the problem? Oh yea I have the Injector/Cam Sync set at +1 it wouldn’t sit on zero if I tried to get there it would jump up or down to +-5 to15 all of a sudden.

I hooked up the MT2500 and there are no codes and everything is in the correct range.
I just remembered that I broke two plugs on different occasions and each replacement is different from the other 4 and each other. Does that matter?

Topic

[college man]

see if this helps.

http://www.ericthecarguy.com/faq/finding-and-fixing-the-causes-of-poor-mpg

[Chris]

Hey what exit?
I forget the exit I was on but it was rte 3
Anyway thanks for the link. I will change the oil and think about a new Thermostat, it does like to be cool.

[zero]

A 25% drop from highway to city isn’t that bad, especially if it was stop and go. I’ve driven several hundred kilometers and had a 25% difference in the return trip because of wind conditions. I guess the important question would be is, how does your mileage track over a long period of time.

[Author]

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