in my old house I would just buy a gallon of lacquer thinner and scrub it as quick as I could to avoid the fumes, the problem is that oil and grease get caught up in the diamond plate part and you have to scrub in both directions. It really stank and gave me headaches sometimes but it was the only way to clean up the oil/grease that was on them. I did it about once a year.
I moved last year and only put my floor down in the last few weeks, I cleaned the tiles with simple green before putting them down (oil got lacquer thinner) and after the floor was down used the Racedeck cleaner, it did not seem to work any better than simple green as to getting things off but the tiles seem shinier. I was going to use rejuvinate on the tiles but the daughters boyfriend broke his transfer case while offroading so we rebuilt that instead and now the tiles are greasy again. Cleaning the tiles is a pain but it is so worth it when I turn the lights on.
In this new garage I am leaving the area under the lift bare concrete, too much oil/grease comes off under the lift, it will allow me to keep the rest of the garage looking pretty good most of the time.