MKL and sparse solvers

What I wonder is: do the sparse matrix routines of CHOMOD and UMFPACK take advantage of MKL
behind the scenes? Enabling or disabling MKL (using MKL) made absolutely no difference when calling cholesky and lu.

Correction: there is a measurable difference in runtimes after all. But a minor one (~20%).
Measured on Surface Pro 7, running Windows 10.