If you want a simple recipe using essential oils for oily hair, add 8 drops lemon essential oil and 8 drops geranium essential oil to an 8-ounce bottle of unscented, nondetergent shampoo. Wash your hair as usual.
If that doesn't work for you, try any of the other essential oils that Aromatherapy for Dummies lists as the best ones to use for oily hair:
To make an after-shampoo rinse for oily hair, combine:
Use the following hair treatment by massaging one teaspoon of the blend into your hair and scalp and leaving the blend on your hair for at least several hours. You can also use the blend at bedtime and leave it on overnight by wrapping your head in a towel.
Source: 500 Formulas For Aromatherapy
Massage the following blend into your scalp for two to three minutes. Leave it for 60 to 90 minutes, and then wash your hair:
Source: Essential Oils Desk Reference
Apply the mask to your hair and leave it for about 20 minutes. Shampoo as usual.
I recommend Young Living essential oils.
Photo Credit: Flickr User UrbaneWomenMag