Make sure that the car you are comparing to is exactly like yours - same year, engine, transmission, trim - these all make a difference in the fueleconomy.gov values. Manufactures can make small differences between model years with the seemingly same spec vehicle, enough to make MPG differences. I agree we should all be using the same "new" standard. I noticed a few vehicles like mine are still using the old EPA values.
I believe playing fair is the only way to go. I have noticed that there are some who only drive less than a mile, or a very short distance, and claim/post their 115mpg or so. Gee, that was great, but I could do that too. Then they are the top dog in a category when it comes to fuel economy. Are they dishonest? Technically no, but this is very misleading. I personally believe things should be documented tank to tank, and not using a
Scangauge or similar for short distance stuff. I see this on other fuel economy documentation sites also.
rant done