I was curious and fired up sbcl:

    * (= (+ 0.1 0.2) 0.3)
    T
    * (type-of 0.1)
    SINGLE-FLOAT
    * (= 0.3d0 (+ 0.1d0 0.2d0))
    NIL
    * (type-of 0.1d0)
    DOUBLE-FLOAT