Because I felt that my Lifetime Average was starting to flatten out, I decided to add a 12-month average to my spreadsheet and chart. In the last year, it's causing me great confusion. Perhaps I just need a reality check. As you can see, it's dropping like a stone. I can't figure out if that's what it's supposed to do or if I'm calculating something incorrectly. Granted, I don't have perfect year-to-year dates so I try to get the dates ranging from "closest to one year ago until today." So my question is this: am I doing this correctly and this dramatic drop is correct or am I doing something incorrectly and I need to fix my math? For all the numbers, hit the link in my signature.
Tony, A quick visual inspection suggests the 12 Month Average downward trend is correct. In general the '09 tank averages appear to be lower than in '08. This might be explanation enough, however ... As to a possible cause(s), could it be an '09 specific condition, one or more of: * "winter fuel" now used year 'round * dirty MAP, (or is it MAF?) the sensor thingy in the intake * reduced capacity 12v battery * new tires Lastly, the HV battery. I've read here that over time it looses capacity, however MPGs are not usually affected. Maybe you have a special case. As to your lifetime MPGs, pretty darn good . Congratulations. :rockon:
No guys, but thanks. I know exactly what's going on with my car and I am comfortable with the regular maintenance that I maintain. I was exclusively referring to the math of the spreadsheet.
It's just that, well, you can see how it's dropping so dramatically in the last year. I figure that it'll probably swing back up but I still find it disturbing. The reason the winter mileage was so low last winter is that I took an "I don't care" attitude." That lasted until I chalked up my first really bad tank and realized that I do care after all.
Are you forced to use an ethanol mix? When were you forced to do so? Was the ethanol percentage constant after that point in time? I have not researched the subject completly but have read many times that the ethanol content is not fixed and may vary from batch to batch (even over the prescribed percentage).
