I always was afraid, too. The important thing is to find an oil light enough, and to use a small enough amount. Start really light - jojoba is a good one. Then start with 3 drops. Then go up to 5.
The best thing I've found to seal with is mineral oil. I don't always use it, but i get the best and most consistent results when I do. It doesn't make me greasy at all - but then I typically use 5-7 drops on my long dense (porous) hair, when it's very wet.
Just give it a shot. Be conservative, and maybe do it on a Saturday when you don't have to go to work just in case.
2c/3a/3b, Fine/med, Dense, high porous, & normal elas.
Lo-poo - Renpure Keratin, SMR, Giovanni SaS
clarifying - mix Johnson's H2T with low poo
Co-wash - Suave Nats. clar. or coco.
RO - GVPCB, Ion Eff. Care, TN.
LI - SMR, Cure Care, or RO
Seal - MO or Jojoba
DT - + honey, ACV, & EVOO to SM masque & GVPCB
PT - Gelatin!, CNPF
Styling - FSG, AIF, BRHG, LALS/PS, GF curl spray gel, SM Souffle/Smoothie, LOOB
Oils - MO!, EVOO, jojoba, GSO, SM Elixer, EVCO, VO5 Hairdressing