I'm struggling with this issue on my 2016 MKX still. I've taken it to the dealer twice with no resolution. They told me to try premium gas, to try gas from different stations, that's it's "normal" for up to 10,000 miles to still be burning off. It is not a mild smell. It's extremely strong and I agree with the comment above that you can not conduct business with colleagues in a car that smells like rotten eggs. I have had many new SUVs and cars in my lifetime that have never had this problem.