Something else you should try, that I just discovered works beautifully on Sensatec seats as well as all other interior surfaces, is a microfiber cloth. You should be able to find them at any major market. You simply wet it with water, wring it out, and wipe down whatever it is you want to clean. It does an amazing job without the need for any cleaners. I took a closer look at my seat this morning and noticed several marks like the ones in your photo, and the microfiber cloth cleaned them off easily (as well as my wife's spilled Frappucino on the center console and passenger seat.

Another hot tip is that these cloths are absolutely the best things going for keeping stainless steel appliances clean and mark free.