If you are talking about putting it on your already relaxed ends, I'd say go for it. Many relaxer systems come with a pretreatment step for this exact purpose. I use Honey Shield from the Mizani line on my ends. I've used oil, and even vaseline in my pre-LCHF days.
Now if you are talking about putting it on the hair you intend to relax I cannot advise you because I have no experience doing it. But I know for a fact that I've read posts about Ladies mixing oil
in with their relaxer. And even the Phyto relaxer system comes with an oil that you can mix in.
I did a quick Google search and came up with one opinion from a Phyto related website:
http://www.whatshebuys.com/phy-ps-64.html
Note: It is never recommended to relax extremely dry or brittle hair. But for those who must straighten their extremely brittle or dry hair, we recommend first applying Phyto's Revitalizing Treatment Oil enough to cover the hair section by section before applying the relaxer. (Intensive Oil Treatment is sold separately and is one of Phytospecifics best sellers!) Once jar has been opened product is good for 6 months (*as long as remainder has not been mixed yet).
So maybe its not such a bad thing. As for your scalp, use a petroleum product. Moisturizer is not gonna protect you.
And I agree with Poookie, DC really well to address your dryness issues. And neutralize like crazy! Maybe even condition before you neutralize as well as afterward. I do that and I think its helpful for dryness.
ETA: Found this blurb on the ph of olive oil. You didn't say what oil you were using to seal. You also didn't say if you were using lye or no lye. But this will give you an idea of how an oil will react with a relaxer. Maybe some of the resident chemists can chime in. In any case, do your research vice relying on opinions.
http://www.oliveoilsource.com/scripts/dictionary.asp?p_do=item&p_id=29
pH: refers to the hydrogen ion concentration in an aqueous solution. Olive oil and other oils are not water soluble so their acidity cannot be measured in terms of pH. Vegetable oils are very weak acids, when mixed with a strong base such as lye they will form a salt (commonly called soap). Better oils have a low acidity while lower quality oils will be more acidic. Their acid content is usually measured in percent free acidity.