I recommend going from least invasive first by using a microfibre dampened with plain water. If that's not enough, then try using a little Neutrogena bar soap (swipe your damp cloth across the bar to pick up a small amount and work the cloth until it suds) to remove the soil. The soap is pH balanced and will not harm or discolor the material. Of course, you have to follow with a soap free damp cloth to remove any residual soap.

I do not use any Detailing Products anywhere in my car's interior - ever. Some of the "cleaners/treatments" actually attack the surface which does effectively remove oxidation, but after exposure to heat and time, the surface will begin to look somewhat melted, less defined and give off a distinctively unpleasant smell. I think you'll know what I mean if you go any used car lot and look (and smell) the inside of a car/truck that's been "treated" with some that famous _______(fill in the blank) detailing product...