I use the FPPF also. Either you have a typo or misread the ratios. The bottle is 32 oz., and treats up to 250 gallons, depending on ratio. I made up a cheat sheet on the additive ratios at
http://members.lsol.net/gop4evr/unlinked/additive.xls
(It's a MS Excel spread)
I based the mileage on the cumulative average of 16.8 MPG for my truck (see mileage spread below). If you use it, you could change the mileage constant for your own experience. I printed out this cheat sheet and plastic laminated it so I can keep it in the glovebox. I have a 4 oz. bottle that I cleaned out to use for this purpose. I fill up between 300 and 400 miles and add one 4 oz. bottle (before filling). Thus, I really don't need the sheet at all. I only have to look at the trip odometer to determine when I add fuel and the next dose.
BTW: I also use the ACT flouride rinse, and I have looked longingly at the measuring feature on the bottle. Problem is, it would take 4-6 measures per tankful, and the bottle would be difficult to fill without destroying it. Sta-Bil and a few other products also make mesuring type bottles that could work . . . .
Just my own opinion. As always, yours may vary
Nels
Manitowoc WI
2001 Chev 2500HD DMAX/Allison 4WD x-cab long box