I have a 2002 1800 with 63,000 showing. It runs great. I bought it about 3 months ago and it was getting about 44 mpg then. I noticed about 3 weeks ago that the mpg was dropping to about 36/38 mpg. It has being riden under about the same conditions as when it was getting 44 mpg. Gas, load and speed was all about the same. Checked the air filter out and it looked to be the original (nasty). Changed the filter and mpg stayed about the same ole 36/38 mpg area. I have been using about 2 oz. of marval mystery oil about every 3rd or 4th tank. Any ideas guys or is this what the bike is going to do with the milage.