Quantitative Observations of Fuel Gauge Segments

Over a one year period (Aug 07 to Aug 08) the odometer reading was recorded as each segment extinguished on the fuel gauge. Attached are the results in chart format averaged over 32 fill-ups (14-15,000 miles); note that the "tenth" segment is when the last pip starts flashing. For those reluctant to open an attachment, the data can be summarized in text format:
1st segment extinguishes @ 128 in summer and 62 in winter
Then the 2nd segment is only good for 27 miles in summer (49 winter)
Segment 3 is the smallest with only 25 miles year-round
Segments 4 through 9 get progressively more distance linearly up to 52 miles for both 8th and 9th.
The tenth and last segment starts flashing on average at 25 miles after the ninth segment goes out; note the tank was allowed to drain to the flashing pip on less than half of the 32 fuelings

Summer started in the last week of April when a 60 mile step increase was observed in the life of the first segment; winter commenced around Halloween with a 34 mile drop in the first segment duration.

Background data:
Model: 2nd Gen 2005
Geographical and climatic: Boston area
Typical mission: 25 mile one-way (reverse, lucky me!) commute primarily on interstate with moderate elevation change
Driving style: Top speeds 65-80 MPH, with frequent high profile vehicle drafting
MPG: average 52 in summer, 45 in winter, A/C used briefly once a week
Payload: one person
Fuel: 87 octane
Mods: Front grill block and snow tires in winter

There must be a similar or more refined study but a PC search did not reveal it. Questions and comments are most welcome.