Yes it loses it's ability to protect the engine and must be replaced, around every two years is the usual time between changes.
old!
Over 40 years old
Yes, it won't hurt.
Regular old green type.
4 gallons Let x be the amount of antifreeze needed to be added. We know that the total amount of antifreeze in the new solution must equal the amount of antifreeze in the old solution + x: .40*(x+12)=x+.20*12 .60x=2.40 x=4 gallons
=To properly flush the antifreeze on a 2002 Yukon you will need a antifreeze vacume system you will need to start the car and have it running turn on all the heating modules to high and have the car reved at about 1.5 r.p.m, or a little higher to activate the vaccume this will start sucking the old antifreeze out. When the radiator is empty{you will know when it is empty because there will be no more antifreeze coming out}you can then fill it up with half and half antifreeze[half water half antifreeze].=
I would recommend the old green antifreeze as the new Dex-cool is garbbage, it contributes to blown intake gaskets and head gaskets.
about 1.5 to 2 gallons at 50/50
To get the proper 50/50 ration, I used an old quart tupperware container. I first poured water, then anitfreeze, then water, then antifreeze, until the system was full.
Prestone extended life diesel antifreeze(red) sold at tractor supply.4 jugs antifreeze + 4 jugs distilled water(sold at the grocery store).flush the cooling system out first(get all the old coolant out first)
replace your heater core and blower motor if nothing works at all. also don't forget to drain your old water and antifreeze and replace with fresh antifreeze
It uses regular old green antifreeze.