"Any ideas on how I can seperate and re-use both items?"
The devil is in the details:
- what is particle size and concentration?
- what is the light oil?
- what do you mean by reusing them?
Depending on particle size (pumped) filtration (paperfilter, colloid filter, celite ) should work as well as centrifugation as was recommended by @Jon Custer. Is it that urgent? Also, cannot you just try it instead of asking it?
What is the oil?
Whatever you do, your graphite will be oily. It does matter if this oil has high-boiling point/waxy components... On the other hand, you may able to use something with low boiling point and just remove it under vacuum / heating, maybe can skipp the whole filtration part.
What do you mean by reusing them?
As I said, there will be remains of oil on the graphite. Also, most probably, you will have fine powder of graphite remains in the oil whatever you do. How do you clean those up it depends on what do you need it for. Do you need to wash the graphite and re-filter the oil? You should know/test that. Also, cost-wise does all this fuss make any sense? Neither graphite nor the oil sound something expensive/special. Also, the more unique, expensive they are, most probably their cleanup will be more demanding (as you need to shoot for higher purity).