I'm running a basically stock 2000 SE 4X4 and am looking into getting the BFG A/T KO's but would like some advice on size. Stock is 265 70 R15 which is close to the 30's - will going up to 31's make a difference with fuel economy? Haven't done the PML yet either - due to this whole gas issue, but have been catching the off-road bug and want a happy medium.