jeff, your method is what i use. Calculate on each fill up

 

19.8 over the last couple thousand miles. Drop of about 3 compared to a year ago and I haven't changed anything but I am just shy of 100k miles now so a tune-up is due.

Mostly stock engine wise other than the exhaust and filter.

 

2003 Monte SS
3800 (Strictly stock, until the spring)
Mobil 1 Full Synthetic
43,100 miles

100% Non-Highway driving MPG (reasonably around the speed limit, but VERY heavy foot):

September '11 fill-ups:
17.19 mpg
18.63
15.62
16.17

October '11 fill-ups:
15.09 mpg
15.21

November '11 fill-ups:
16.89 mpg

Then this past weekend I took my first roadie out on the New York State Thruway. Speed limit is 65, I roll cruise control between 71-72, but my heavy foot, admittedly, still creeps in WAY too often ... even on the highways & bi-ways.

22.84 mpg



Either way, I want to thank @Scooby Doo for beating me to the punch & saying that the overhead console 'computer' is SOOO far off when it comes to keeping mileage ... It is in fact so far off that, I am sorry if this offends some, I snicker(ed) when I read some folks here relying on those numbers as if they were the gospel.

The ONLY legit method, as MANY others have stated in this thread, is to note miles driven, & divide by gallons burned.

If anyone is interested in insane number crunching, etc., there is a fantastic 'lil app available in the Android Market called "FuelLog". A basic version is available for free, but, of course, a very feature-rich version is available for a few beans. The premium version offers every single angle of fuel consumption, automobile costs, & graphs galore, etc. that will keep anyone like me busy for hours, if they so choose to engross themselves in it. It will also save to a file format to export to Excel, OpenOffice.org, etc. It will also keep track of multiple vehicles. I have 7 vehicles I am constantly archiving, & I can add more at any time ...

 

As far as tracking fuel economy i made myself a spreadsheet. I have the dates, price per gallon, number of gallons, total cost, mileage, distance driven, mpg and a constant running average.

 

Been getting 25-27 on the Highway to and from work 57 mile round trip.

 

i get about 26-28 mpg city and high way for the 3.5 i keep forgetting what that engine type is. but it kinda sucks wish i could super charged it like my mustang i get about 33 city and high way. all i know synthetic does help keep every thing running low on rpms when ideling and driving threw the rpms

 

you can do all that stuff electronically online. click on my fuel economy banner in my sig. it's pretty slick. when you fill up at the pump just text your miles, price, and gallons to fuelly and it does all the calculating for you.

so looks like i'm gettin 24 mpg. i do a lot of mixed driving. majority highway.

 

some how i am getting around 27 mpg or so i not sure how and its a 95 with a 3.1 is this posabable for real and i still step on it once in a wile?

 

depending on the speeds your doing and the mileage you have it sounds reasonable. I'm getting 25 sometimes 26 mpg cruising at 70 with a mix of highway and stop and go traffic

 

Thought i posted

Monte: INFINITY MPG Best mpg ever! no if i could just drive it....
When it was running 17mpg best 50/50 hwy/cty

when it was delobed on the one cam lobe it and i was still driving it the thing got 9mpg.... on the same drive

Intrigue 22ish have yet to really calculate it