I have suddenly noticed a major dropoff in MPG, and the timing seems to correlate with my last xcursion. Background info: My X has 3k miles, is about 2 months old, and hasn't been in any shop since it was driven out of the dealer (am going in for an oil change on friday though). I have kept track of gas mileage since I purchased it, and I was pretty consistently getting 17 MPG. I then went on an Xcursion a couple weekends ago and am now getting 13 MPG

. Can anyone think of a possible reason for this (mud, something jiggling loose, damage from hosing down engine, etc)

? I also moved to a 31" tire at the same time but my speedometer seems to be right on and i don't think it would account for 4 MPG difference.
Thanks