I think I've totally put my worries about "clashing" add-packs to the wayside... While there is certainly evidense from Bob- that some certain aftermarket addatives can have unwelcomed effects in certain situations(lucas)- but Typically any bottle of motor oil will state, on the back somewhere, that it is fully compatable with other motor oils. leading me to believe, that for the most part, there is no "significant" danger in "mixing" different breeds of oils. We have a large number of folks here on BOTIG who do their own "mixing"... redline+havoline+mobil etc etc, to create some "ultimate" blend that they like the thought of, and they aren't having any problems. For all we know, they may be acheiving a higher level of oil quality in doing so. taking conservative amounts of the benifits from different oils and mixing them to create a good all-around oil.
You could do just about anything ya want with the green and gold- heck, you could use the green 1 quart at a time mixed with 4 quarts gold on each change. While the formulations are a bit different- more than likally both oils will perform very well in just about any engine calling for a 30wt.