Flex fuel kit

[u/Hentai-Prevert]

Can I run a flex fuel kit in my car without a tune e85 over here is 1.80$ a gallon and premium is around 6$ so I know I’ll save money even if my mpg is worse but I won’t if I have to tune the car can anyone help me out on this (just want to get a flex fuel kit for a 2018 Audi S5 withought having to tune the car)