I hear you're not supposed to mix the water and oil but I have before and it never caused me any problems. It may be because if the V gets caught up in the slower dispertion of the oil there's a SLIGHT chance it may go bad and cause an infection since water tends to be a little dirtier. Just my hypothesis.
Flex and Mustang already said it, but I will say it again: Less injections=Less chance for infection. Also winny has been rumored to have an increased chance for infection when injected. So why risk injecting when it is not necessary? Obviously, there are less risks involved when drinking winny as opposed to injecting it.