4T is definitely a great oil. It has proven to work for me in every application i have used it for. From 3 Hp to 35.
Since all engines have some blowby it will turn varying degrees of white or pink depending on how much methanol leaks past the rings into the crankcase. Since a methanol engine uses a AF ratio of somewhere around 6:1 as opposed to gasoline with a ratio of more than twice that, methanol is going to get into the oil. It is not a PAG oil like many of the other kart racing oils. Methanol will mix with PAG oils and you will have no idea of how much methanol is in your oil but it will be there diluting and reducing the lubricity of your oil.
In my opinion the fact that the Briggs oil turns pink when you use methanol is a good indicator as to how much methanol is in your oil.
No matter which oil you use i would definitely suggest you change the oil at the end of each race day since methanol is hygroscopic (it absorbs moisture / water) and there is a lot of moisture in the air during most of the racing season.
The nice thing about 4T is that it has a rust inhibitor in it while PAG oils do not.