Can you use a steam cleaner on engineered hardwood floors?

The short answer is no.

Often steam cleaners say they can be used on "sealed" hardwood. Wood floors are put down in planks. Every board has a small space between them. Especially in winter when the humidity is lower, these spaces shrink.

A steamer is forcing water vapor into these spaces. The surface may have polyurethane, but the sides do not.

If this isn't enough to stop you, then remember wood flooring manufactures void warranties on product where water has damaged them!