What are the stock struts filled with, gas or an oil substance? I have some thing leaking what looks like oil right behind my rear left tire and I seems like its probably the strut. Are they filled with oil?

 

Most OEM shocks are oil filled. The only way to really find out is to take the strut out remove the spring cause you going to have remove the dust boot that is in the way and check if its leaking from the pistion. unless the dust boot is already destroyed then you can just look right at it.

 

The rear suspension uses shocks not struts, and you need a new one