I keep making the same mistake. It's Fleet CHARGE, not FleetGUARD. Fleetguard is a brand of filter.
And as usual, best deal is Advance Auto. $16/gallon, but code TRT30 is ALWAYS in effect, 30% off, takes it down to a shade north of $11/gallon. If you're in the midwest and near a Mills Fleet-Farm, it's on sale there for $12/gallon at the moment.
Edit - be VERY careful selecting Fleet Charge. They do make a 50/50 diluted version, and the label and bottle look ALMOST the same. Make sure you know what you're buying before you pull the trigger.