12 mpg is pretty good unless your drive solely at 55. It could just be bad gas

 

If he didn't mention the plate it's pretty safe to assume he didn't get it fixed right. Since most shops don't know about the permanent fix they put it back to factory spec using OEM equivalent parts, but just keep doing it over and over every time it blows.

You could easily find out what's in there with a magnet. Steel is stock, fixed is aluminum. A magnet wont attract aluminum.

Chances are it wasn't fixed right with the aluminum plate and you now have a blown plenum gasket again. With your mileage I'd first verify compression to eliminate the possibility of cracked heads and/or worn rings and if it checks out then do the plenum fix and new timing chain. With those fixes it would likely run like new again if there is still good compression.

 

^ This along with, 1) Winter blend gas stinks compared to spring blends. 2) Your pulling in colder more dense air, means more gas will be used to compensate for the increase amount of oxygen. 3) (this one is just a though really) If he changed the plenum, did he make sure the cat wasnt clogged. If it wasnt clogged then, see if your plenum is blown again and check the cat now. 4) Your ram will idle higher during open loop to try and warm the ram faster.

Tons of other factors, but in the end, 6 mpgs is really low for our rams.

 

2nd gen rams get the worse mileage out of all of them to begin with but 6 is pretty bad.
I get 10 to 11.5 in town with mine.

 

No, colder air is less dense. Why else are people always installing Cold Air Intakes on their vehicles?

 

Back to fifth grade science class for you!

 

O2 sensors would not really be the culprit because the engine stays in open loop longer due to it taking longer to reach operating temps. A LOT LONGER.

But they probably do need to be replaced. Like was mentioned, winter blend gas is horrible for gas mileage, and if you warm up your truck, you are wasting gas.

6mpg on a blown plenum truck in the winter (warming up before driving) is not that far off. I was at 8.9mpg with my truck when it was stock. But my commute to work was only about 1 mile last winter. Now my truck is right at 11 MPG in the city.

Also, if you travel over 65 MPH, our trucks get single digit gas mileage.

 

Except they replace the one time use bolts with new ones that are the correct length which despite what the Hughes marketing dept would have you believe was the actual issue which dodge admitted to... The bolts were too long bottomed out before applying enough compression to sandwich the the gasket to hold it in place... Besides what I've seen here I have also been told by actual shops and mechanics who have replaced the gasket and used the correct bolts that the issue does not return once this is done. with so many opinions and testimonials going each way its hard to believe whats right or wrong.... as far as mixing diffent metals and different expansion and contraction rates you would think this would cause lots issues on other vehicles with steel against aluminum... I have steel heads on a magnesium block vw with aluminum carb manifolds how does that function well? and I'm pretty sure my crappy crossfire vette uses a steel throttle body plate on an aluminum manifold?

 

Right, I neglected to mention the proper length bolts. I should have said the plate kits, which all seem to include the new bolts.

 

My point is there seems to be little if any evidence out there that the real issue wasnt just the long bolts and the whole thing can be fixed right by just replacing the gasket and using the correct bolts with the OEM steel plate at a huge cost savings vs buying the pricey aluminum plate. So far the people I that have mentioned they have done this all seem to not have the issue come back. Or if it does I have missed the threads stating that. Its such common practice to promote the Hughes plate kit I think most do it here with no first hand experience on the subject...they just parrot what they have read.
I have the stock plate in mine and I assume the PO replaced the bolts and gasket because at 140k its holding up fine right now knock on wood.
On another note winter gas does suck and I read here that the 180 degree thermostate can cause the truck to never reach optimum operating temp and therefore the computer tells it to run rich...
I did the seafoam treatment on mine last year and noticed it ran much better afterwards.(smokes like a bitch thoughwhen doing it).. It can even burn some of the carbon out of the cat I've been told to help if its restricted..