Every carrier I've operated with uses the "standard" formula of $1.25 fuel and the ones I recall were 6, 9 and 15 mpg for tractor, straight and van. Plugging in the $1.25 base to the OOIDA site and 15mpg for a van matches the numbers I last used. I believe at least some carriers are now doing two different formulas for vans, one diesel and one gasoline. I don't know what those are as that change was after I quit driving. FSC should never go below zero although probably at least a few carriers will go negative if they think they can get away with it. Kind of like QC fees.