For the Mike E post, there are actually 10 quarts in 2.5 gallons, which means at 32oz per quart, that's 320ozs. Mix at 40:1 divide 320/40=8oz
For 50:1 divide 320/50=6.4oz
His math is right, but the ratio was wrong. 192ozs is for 1.5 gallons.
Bob J, November 2013