Question 1200059
Simple dilution with water
w gallons of water to add


{{{(1*1.00)/(1+w)=0.85}}}

{{{0.85w+0.85=1}}}

{{{0.85w=0.15}}}

{{{w=0.17647058823529411764705*gallons}}}{{{calculationonly_unrealistic_accuracy}}}


Better to say,  about 22 or 23 fluid ounces of water