Julia optimisation difference

When the following code is run
x = muladd((5270536651468945146),(π),13656)
println(x*(10^-19))

it produces 1.6557879224730618 at optimisation level 0 and 1, but it produces 1.6557879224730616 at 2 and 3. I know the precision is not a massive difference but wanted to flag it anyway.