Can I apply minoxidil solution while there is a little hair oil on my scalp ?

You won't offset the effects of Minoxidil using it that way. For best results, a combination approach is best with Minoxidil along with prp and progesterone injections and/or hair transplantation. I recommend a formal consultation with a hair loss expert. Best, Dr. Emer

yes, it is best if the scalp is as clean as possible, but a little hair oil should not affect the absorption of the minoxidil

You ca apply minoxidil to oily hair without any problems.  We usually recommend using the minoxidil twice daily and if you want to stop to do it gradually.