How close can you get to the bottom before you run out....

[nitrofarm]

I drove mine dry last week as I had been having issues with cutting out below 1/4 tank. I replaced the strainer, pump, and filter. So I was testing low tank and drove till it stopped. I put in 2 gallons, drove 4 miles and put in 7.6 more. And no sputtering until the final time.

Sounds like you have @ 9.8 usable fuel,and thats what I've come up with also.