I am getting ready to do the first oil change since I have owned my rhino. I remember the guy I bought it from saying that he was running ams oil in it but I read that some people are running rotella which would be better for me since I already run that in my boat. Is there any harm in switching it without flushing it? Also how much oil does this thing hold? I do know that it needs to be FULL on the dipstick before every ride but not sure how many quarts full is. Thanks.