My experience and 2 cents:

When was the last time you seafoamed the carbon or ran injector cleaners? I do it every couple oil changes.

I recently replaced the MAP sensor as they do get old. The diaphragm inside gets brittle and won't read properly. There is a big thread on it in the Durango section. I noticed a wee improvement in drive-ability, mileage and the cruise is more responsive.

Copper plugs only last about 30-40k so replacing them at 20k is no biggie. Get stock CHAMPION RC12YC for best mileage.

I use a drop in K&N filter. Helped throttle response.

Pump tires up to 45-50psi. I run E rated tires and keep psi in that range.

When was the last throttle body cleaning? I do that every two years. Get's real black and nasty. If never done, check out my sticky in the DIY section "clean your throttle body!" Helps performance and mileage.

Do you have stock exhaust? When I replaced the stock muffler years ago, I gained 1mpg. When I hacked off the stock cat and went with Magnaflow I gained another 1mpg.

Cap and rotor should be brass from Napa or equivalent for best mileage.

How old is the t-stat? If it isn't working properly anymore it can affect mileage. I just replaced pump, stat, hoses and coolant and it warms up quicker allowing closed loop operation faster.

How much weight do you carry? Miscellaneous junk, tools, clothes, etc. in the back or bed will definitely cause a drag on mileage. When my first tool box was stolen, I removed everything from my truck and it ran like a puppy after getting a bath.

That's what I can think of at the moment. My truck is over 200k and gets 13-14 in daily driving and 15-16 on the most recent road trip. Yes, it is a manual, but I've never seen it below 11 except when towing. It has a small lift and runs 285s on 3.5 gears. Hope this helps!

 

Very good information.

As for the cleaning, I cleaned the TB when I replaced the plenum, I could have done a better job after reading your article on it, and I try to run seafoam with each oil change and I used Chevron's Techron injection cleaner earlier this year. I do try to run this kind of stuff, not sure if Techron is the best, but I figure it is better than nothing.

I have been considering a new filter, I am leaning toward the Spectre over the K&N simply because of the price (plus I am reading that it performs just as good). Exhaust is stock, it looks like the previous owner replaced the CAT (if not multiple times) and the plenum was blown so the exhaust probably has some crap in it.

I replaced the thermostat, pump, coolant, and hoses fairly recently. I don't carry that much stuff around with me, really just a small Harbor Freight toolbox. Considering the plenum was bad it may be a good idea to just go ahead and replace the plugs, and I may do the wires and cap/rotor too, just wish I had done it when I had the intake manifold removed. I think I may do a bit more reading on diagnosing a bad MAP sensor and see about replacing it too.

 

Make it a rule that you fill with only Top Tier gas and you won't have to fool with cleaners or bottled additives -- unless you just like pouring stuff into the fuel tank so much that you're willing to waste money doing it.

The problem with cheap gas is cheap additives that become harmful to your engine when they and their combustion by-products foul the engine oil by way of the blow-by stream. You can dump Techron into that cheap fuel to keep your injectors and combustion chambers clean, but it won't stop the cheap additives from entering your blow-by stream so what you get for it is an engine that dies prematurely with really clean combustion chambers. It's a helluva lot better than not dumping Techron into the cheap gas, but you're better off not having cheap gas in your tank in the first place.

You'll get better fuel efficiency out of Top Tier, too.

 

I run only Shell or Chevron and seafoam a couple times a year. It always produces a nice big cloud no matter the quality of gas I've been running. Of course, I've been using it since before we knew what a plenum was, so I guess I'm a fan after all these years.

The cap and rotor is really not bad once you get a feel for it. I just threw a new set on before my trip last month but it took a half hour while I helped a neighbor with her car. Just crawl up on the engine prone, and stick a flashlight back there. Then hold the new cap behind the old one, and transfer one wire at a time. There's just enough room to do this. Remove old cap and discard. Then reach down, pull off the rotor, pop on the new one, seat the new cap, and tighten her up. Like I said, if I wasn't distracted during, it would have been less than 10 minutes.

 

Lucky you get 9-10mpg, i get 6mpg with my truck

 

Check your plenum. You should at least be able to get into double digits.

 

Even with my front axle locked in? Got 200lbs of tools in the bed as well, never got above 12mpg. To top if off i live in a very hilly area. Truck has lots of rust but only 102k

 

Why is the axle locked in? 200 pounds of tools shouldn't make any difference at all.

 

My vacuum lines rotted off so my CAD is in the position where the intermediate shaft is locked in with the center shaft

 

That's easy enough to fix. Vacuum line is dirt cheap at the local parts store.