you might want to send a small sample away to get analysed. stick into a clean PET container ie plastic coke bottle, wrap tape around the screw top and package it well. most of the oil companes will do this for you, pretty sure duncan has had it done.
oil usually burns grey/white and fuel black, not sure what brown means. have heard various reports re pennzoil, a search should turn up a few comments.
not sure what 'car would r and r' means?
cheers