I use the dilution ratio that is on the soap that I am using. DP Extreme Foam says 2oz per 6 to 8oz. I was disappointed in the foam created even at max foam. So I would add more soap. I found that I was expecting too much from my Foam Gun. Oops, just re-read the title. Actually just got my Foam Cannon last week and have yet to use it. My brother inlaw found a pressure washer at the company he works for that is a transfer station for trash. So, I went ahead and bought the cannon. I can't wait to use it.