Hi guys, new to the board today. NOT a mechanic! I'm on my 3rd Dodge truck, this one is a 2001 off-road I bought new. Been an awesome truck. I put BFG AT315's on it last year and they are OK, (rub a little at max turn, no big deal). But my gas mileage dropped. What gears am I running stock? Are they 3:9? 4:10? I'll be going back to the stock size tires next time but these have a lot of miles left on 'em. Should I change gearing?

 

Check in your glove box or under the hood, there should be an options sticker that lets you know what gears you have.

 

If its an Off Road, they're 4.10's which isn't to bad, but 4.56s would be a little better. Not sure how much you'd gain by stepping it up one. If you were going from say 3.55 or 3.92 it'd be a bit more economical and you'd notice a bigger diffrence.

 

Yes, I found where it said 4:10's. Probably wouldn't be worth a change, other than back to original tire size then?

 

When was the last time it had a tune up? Is your plenum gasket leaking? Is the air filter clogged?

 

Minor tune up a couple weeks ago with new plugs, wires, cap, rotor, air filter is clean. Never noticed the plenum leaking, where would it be evident?

 

One of my off roadin' friends runs an '01 shortbed offroad....gets about 13 mpg with the 4:10s and 315 Goodyear MTRs. He is also running a catback with dual outs and an Airmax CAI, which he claims increased his mileage. If you have a quad cab, it weighs about 700 lbs more, and that can affect mileage.

Checking the plenum is easy. With the motor off, remove your air cleaner assembly and open the throttle all the way and shine a light into the intake manifold....if things look oily or oil stained, your plenum is leaking.
BTW, you did a tuneup, but try changing your PCV valve. I've seen certain vehicles pick up a couple mpg by doing that.

 

No, as far as I know it's the original PCV valve. They're cheap, I'll throw a new one on. And I'll go ahead and switch out the IAC while I'm at it. I'll have to take a peek down through the throttle body and see what's up? I take it this is a common problem with the 360?