Q4 I have heard there are a number of additive types available. Which should I use? The commercially available additives are either phosphorous, sodium or potassium based.The phosphorus based Valvemaster product has been extensively tested and proven to offer superior efficacy and performance to either the sodium or potassium based VSR protection additives. Valvemaster has passed the draft Australian Standard for lead substitutes AS4430.2. In New Zealand, Valvemaster has been used almost exclusively since 1996 and with many of the common older UK and Australian car models designed to run on leaded petrol.