Folks - I have noticed over the last 2-3 months that my 2001 325i is giving a much lower mpg than normal. During my regular commute I was able to get about 400-420 miles per tank, and am now getting 340-350 miles. Nothing has changed, same commute, traffic patterns, gas used, etc. I understand variations in driving conditions, but this seems like it happened overnight and never corrected. I am continuously getting 340-350 now. that is an approximately 15% delta and is big

Any theories on how and why this can happen?