I will be using the Trilene 100% fluoro and I have used 8 in the past but wanted to try heavier line on them. 

What is the highest you have used?

It depends on the size of the spool. For a typical 2500 size spool, I wouldn't go higher than 8 for FC or 10 for mono.

It depends on the reel capacity... Look on the side of the reel and it should tell you the suggested line sizes. If it lists 4, 6 and 8 lb, then only use max 10 lb. and minimum 4 lb. on it. Trying to use something like 15 lb test on a reel stated for 8lb will work but a big fish may strip the gearing or mess up that reel since it is not made for heavy duty drag from a 12 lb+ fish.

The only exception is braid which has a smaller diameter so you can use larger test.

You need to consider the diameter of the line since each company rates their lines differently. You might only be able to use Company X's 10 lb. line on a spinning reel, but if using Company Y's, you might be able to go up to 12 lb.

The line numbers on the reel have nothing to do with any rating system. It is there to let you know how much line of the common diameter mono lines in each listed pound test that the spool will hold. Nothing more and nothing less.

My dad uses 17lb minimum on Pflueger size 40 spinning reels for bass fishing.  The reel specs really have nothing to do with what you can use.  A 12lb+ fish can strip just as much drag with 8lb as it can 15lb line.

i have a 2500 size reel and use 12lb for finese even though everyone recommends 10lb.  i use 12lb because i already have and am using it up then ill put 10 on it.

I've put 8, 10, and 12# Trilene 100% Fluoro on 2500 spinning reels, and the only way I could get by with the 12# is when I soaked it with line conditioner twice a trip.

I'm sticking with 8 and 10#, or better yet 15-20# braid and a fluoro leader.