Your opening post said that you have had a significant change over a short period of time in your coolant level.

Prudent course of action would be to get the system pressure tested for any leaks. Even better would be to put preessure in the system and let it sit for a long period.

If no leaks then monitor for the same period with regular checks. If still losing coolant then it must be going somewhere.

Combustion can and does consume coolant if there is a gasket leak.

As an aside, I have just had my 4.8 opened up after 25,000kms whilst looking for a reason that it is detonating (pinging). They found that the head gasket was showing signs of coolant leak, of an area approx 1-2 inches near the cylinder. One can only imagine what it would have been like after 100,00kms..... (blown gasket??)

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