question about ground wire ( 8AWG WIRE )

i have 20 feet of tsunami comp series oxygen free 8awg wire laying around and i am thinking upgrading my ground wires on my 89 XJ with it?

this wire was left over from one of my amps and i want to know if 8AWG wire is good enuff to use for a ground

Yes it is adequate for most of your grounds except the main battery ground.

I wouldn't bother with anything smaller than than 4awg, but this depends on the amount of accessories that you're running I guess.