I have recently ran into this same problem....I have over 1000 sqft of tile in our home. My daughter bought me a steam mop for Christmas last year it only pushes the dirt around. I have tried just about everything. I tried my oover carpet cleaner but the brushes aren't stiff or long enough. The other day I had a thought of spraying Windex (Original) on the floor and using a long handle scrub brush....Amazing results after you let it sit a few minutes, use the scrub brush and rinse with really hot water with your good old mop and couldn't believe hour it cleaned the grooves and the grout....I will continue to use this method until I have it all looking the same...We had recently moved into our home and the tile is beautiful but needed to be deep cleaned....Smells good while doing it....