Cleaning the underneath of the car question?

[oxw01svt]

I was wondering what everyone uses when cleaning the underside of the car. i figured i could use brake clean on the really dirty spots cause this is the first time im cleaning underneath the car and its an 01. So i sprayed some brake clean on a rag and started in a small spot. It looks like it was starting to remove paint, is this a protective coating of some sort to prevent rust? So then i tried simple green dilluted and the same thing happened. Should i just use soap and water? And if theres anything that some of you can reccomend to do i would appreciate it thanks guys.

Heres a picture of what im talking about.

 

[hoofbeat]

:beer:Brake clean is a solvent probably not good for your paint. I have used a 50/50 mix of Simple Green and water with good results.

 

[jtm]

i picked up some cleaner for my power washer at lowes/home depot, it was called multi purpose cleaner for general cleaning. like 5 bucks for a gallon, i diluted it in a sprayer and use it all over,tires, inner fenders, even along the bottom of rocker panels, and pre treat front bumper when its caked with bugs. seems to work well and its super cheap

 

[blown up 98]

i use simple green max diluted 1 to1 and it works great. the bottom of my car is a green color about like the spot you have marked do i dont know if yours is different.

 

[oxw01svt]

i think i might have confused you guys with the picture. its not actually the Oxford White paint on my car underneath on the side skirts. its the primer light gray looking paint on the floor panels. the picture above is actually the frame in the rear that has the black styrofoam attached to it. Is our cars sprayed with a rust prevention paint underneath? That is what is rubbing off when i tried even with simple green.