Garlic oil is very useful and I make it whenever garlic is in season.
Since it's a bit of bother, I make it with oven-cooked garlic.
This recipe produces a non-bitter and simple garlic oil.

Tightly wrap the garlic in the aluminium foil. If the juice leaks out, it will be smelly.
This will not turn solid when stored in the fridge. It can keep at room temperature for a month. Store in the fridge in the summer time
If adding chili peppers or herbs, dry them well before adding. Recipe by Wanko mama