Here are the facts:

1996 Toyota Tacoma regular cab, 2.4l, 5spd, owner's manual says I have a 15.1 gallon tank.

I tanked it up over a week ago and kept track of mileage at exact tank marker points (E, F, 1/2, 1/4, 3/4) and then based on fuel mileage for that tank, calculated how many gallons I had at each marker, I even took a few pictures.

The assumptions are that I drove relatively constant throughout the whole range of the tankful, which I did, daily commute, no A/C yet.

The conclusion is also in gallons to rule out odometer error and the assumption is that the measure of fuel at the station is accurate, I filled up at the same station in the same way both before and after.

The results:

F = 35 mi

3/4 = 90 mi

1/2 = 180 mi

1/4 = 275 mi

E = 330 mi

When it was finally time for a fill, there were 353 miles on the tank.

Here is how the gas gauge looked before the fill:

Kind of overdid it, minor ecological distaster at the station, but...

Anyways, even with overfilling, 12.9 gallons went into the tank, was still 2.2 gallons short of bone dry and still below E.

Here is now the approximate fuel left in the tank at all points:

F = 13.8 gl

3/4 = 11.8 gl

1/2 = 8.5 gl

1/4 = 5.1 gl

E = 3.1 gl

The above numbers are probably +/- 0.3 gl, your mileage may vary.

So between above F and F, about 1.3 gallons, between F and 3/4 about 2 gallons, between 3/4 and 1/2 and 1/2 and 1/4 about 3.3 gallons each, and again between 1/4 and E, about 2 gallons.

The fuel gauge appears to be symmetrical and also proportional to the spacing between the lines, see pic. above, the only exception is that on the E end, there are an extra 2 gallons.

***And as an added bonus for those who like to top it off until the fuel spills out, I tested to see exactly how much the difference was between a normal fill (2 additional clicks after auto shut-off) and spillage. At the local Shell station here with a fairly fast pump, that difference was exactly 0.12 gallons, approximately 0.03 gallons ended up on the pavement, see above.***

Hope this is useful, entertaining or perhaps annoying at least to someone, it was fun to do.

Chipsndukes