Alright, the vehicle in question is a 2001 2WD 2 door Blazer. I don't record my mileage but I check it every tank just to look for obvious changes. A tank back i got 12mpg as opposed to the 16-18 I'm used to. So I filled up, chalked it up to aggresive driving and decided to run a conservative tank. Well I filled up last night. 12 mpg again. I have noticed a speed sensitive humming noise.
It audibly kicks in around 30mph and gets louder and higher pitched the faster I go. At 45 its very audible.
Any ideas where that could be coming from? I thought maybe a brake isn't releasing from the rotor or something but then i would expect the car to pull one way or the other, which it doesn't. I'm supposed to be taking a 4 hour drive for thanksgiving in 4 days and i'd like to avoid burning through a bunch of gas needlessly.
Any ideas or suggestions would be appreciated!

FYI: Only mod is a cold air intake and its been on for a while. The rest of the car is bone stock.

Anybody have any ideas what could cause this?

wow... i have no clue.. thats really odd, even tho this is about a mid size/compact truck, this would be almost better if it was moved to the general or perfoamance section...

i'm trying to think of what could a humming noise have to do with acceleration and gas mileage... but nothing really comes to mind... possibly an intake leak? like the throttle body? but wouldnt you be throwing codes?

if it doesnt have to do with the noise than i'd say that maybe it has to do with a fuel sending problem... if you happen to know someone that wont charge you much for a diagonostic check up on a dyno than you should do that

Getting it on a dyno won't be easy or cheap for me. I haven't really felt a loss of acceleration. Just that obnoxious droning noise. No obvious intake leaks or anything. I was down a bit on coolant but thats kind of an unrelated issue that was easily resolved. So i'm at a complete loss. Again, ideas are welcome!

idk what else to tell ya...sounds like maybe a fuel problem... can you diagnoise exactly where that noise is coming from.. like under the floor, motor, front, rear?