Cetane additives

Thanks to all for feedback on my earlier post concerning Power Service additive. Before I get a second additive to improve cetane, has anyone received additional information from PS, or otherwise know how much of a cetane improvement the PS (white bottle) additive provides? I guess a partial answer to my question might be "not much" since, as gardentender indicated, PS makes a separate cetane additive in a silver bottle.

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2000 Black on Black Golf GLS TDI
Five Speed, Heated Seats, warm tush

Mel:

The reformulated 96-oz white bottle of Diesel Fuel Supplement gives a 2 point cetane boost and treats "up to" 300 gallons. For a 4 point increase, you need to double the doseage, so naturally it only lasts 150 gallons.