Over the years you will lose refridgerant via leaks in the system. Its like death and taxes.

You also lose oil via the leaks.

If you keep refilling the system AND don't also add oil you eventually run low on the oil and the system self destructs.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)