Its time to change my oil....I currently have plain old motor oil in my 84. My intention was to use this as a sort of flush for a 1000 miles or so, and then change to Royal Purple and a K&N filter. I overheard a conversation teh otehr day where one guy told another you have to "flush" after dumping regular oil or the Synthetics will foam up. Is this trueor a lot of BS?? If so, what do I use for this??