How many grams are in half a cup in oil?

It depends on what type of oil you're using, as different types of oils have different densities. Assuming you're using canola oil (which has a density of .92g/mL at room temperature), you could find the value in grams using the following ~

1/2 cup = 118.3mL

D=m/v

.92g/mL=m/118.3mL

m=108.8g

So in short, it's about 110g of canola oil