Diluting it will raise the freezing point. But it will already have some
water in it so simply mixing it 50/50 with more water may not equal -25.
Look at the manufacturer's site and see if they have a chart on diluting it.

"Eric G." wrote in message
news
For many years I have winterized my boat systems using -25 degree RV
antifreeze. For some odd reason I can find only -50 degree antifreeze
this year. I don't need the extra protection (or expense since I use
20 gallons of antifreeze) since my boat is moored in a location with a
moderate climate. Is it safe to dilute the -50 degree antifreeze with
about 1/2 water to get me to approximately -25 degree burst
protection? Thanks for any input.