LG pre-washes with cold water
I recently got a used LG front load WM4200H so I've been experimenting with the settings. That also brought me here where I learned about Biz and citric acid and washing on warm not cold.
So I decided to run a load of my dingy old white tee's to see if Biz could revive them. I used the "Bright Whites" setting on the LG (hot water temp) and added a pre-wash to give the Biz longer to work. (no "soak" setting on my model)
To my surprise, the pre-wash filled with 23°c water! It also drained that water after the pre-wash, before refilling with 44°c water for the main wash.
And looking at the hoses under the top cover I should have known, because there are 4 hoses, with one labeled "pre-wash" that is only connected to the cold tap.
So that tells me the pre-wash may only be helpful on clothes with a lot of soil like dirt and mud or something that needs to be diluted with extra water. It doesn't give the enzymes or oxygen bleach in Biz any extra time to work.
Instead I'm probably better off using the Heavy Duty cycle and/or setting the soil level to "high" to buy some extra time?