99 Mercury grand marquis, 4.6 V8.
Flushed out the original coolant from 1999 when I got it last year. it was horrid. Put supertech coolant back in. 6 months later I decide to put a new water pump in it since the bearings were a bit worn. Coolant was dirty, but not as bad as original. It's stayed clean since, but the hoses look like a clogged artery from deposits and can't get the reservoir clean plus I can see sediment still floating around. Have new reservoir and hoses to install. Going to flush again and use Zerex G-05 this time and install a coolant filter. This was a bad one. Only neglected part of the car, very nice otherwise. Luckily the coolant passages inside of the engine block look relatively good. Nothing super rusty, and the original heater core is capable of putting out 170* F vent temps.