[JRTJH]

If I don't use the compressor first, I need about 4 gallons to do my trailer.

If I use the compressor and blow out the lines, I don't need quite 2 gallons. That includes all the traps, the toilet seal and some left over to pour into the toilet halfway through the winter.

For me, I don't like pouring the antifreeze on the ground (pouring it into my septic system is effectively the same thing) so the less I use, the better I "protect" my well water from ground water contamination....