At our dealer we use just 1 on a normal every 2 year flush. But if there was a running hot or scale problem we would use 2-3 depending on cooling system capacity. Of course mix in a gallon container with hot water, & then pour into engine.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V