Left over oil and what to do

Have two cups of cloudy canola oil from the frying last night (eggplant). Strained it but it is still dark. Can this be used again - or lightened some way? Is it OK as is.

You can use it again, especially in small doses. After I fry something I just leave the oil on the stove top and use a few spoonful at a time when I'm stir-fring something. After a few days, sometimes weeks I usually use them all up.

Or if you mean can you use it to fry again, you can, but your food will turn dark fast and sometimes that might leave the inside still uncooked.

My mother fries slices of fresh potato in used oil to clear it--a solution that has worked for her for about 65 years. Back in the depression, the idea of throwing away perfectly usable frying oil was viewed with horror.