Worked with my sending unit couple hours this evening trying to get it to read 1/4 with exactly 4 gal. gas. Did manage to get close. But when added 4 more gal., hoping for 1/2 then, it went on past. Closer to 3/4 if not a little above. Mine is earlier model than yours though, who knows if they even use the same sending unit.
Manual that came with car tells about watching gauge as you fill it up from empty. Taking note of gallons put in, and reading of gauge at 1/4, 1/2, 3/4, full.
I don't think each point will be the same amount of fuel.
Take sending unit out and see where float is positioned compaired to sending unit mounting area. Measure tank depth also, so that float arm doesn't hit stop tab before gauge reads near empty.
Best of luck,,, I don't think these things are very accurate anyway.
