As costly as Evaporust is, it's cheaper than an engine rebuild.
I think I'd try some more usual coolant flush product before deciding it needed the Evaporust treatment. Like 2ManyTrucks said, if there's a lot of rust in the system it burns thru the Evaporust in short order. Even if you do use it, it would be better to flush the block with cheaper stuff first to get all the loose rust out first.
