Funny you should ask that, just this weekend I did the Distilled & RMI switch from the Winter Distilled with anti..anyhow, I used an OLD (2 years on the shelf) bottle, and it appearded to have settled into an oily sheen on top and the yellow RMI on the bottom. I know cause it FREAKED ME OUT when I began pouring it in and it looked like MOTOR OIL for a brief moment. Either way, I only used about an ounce from that bottle and discarded the rest! I'm thinking it must have sat on Jack Cottons shelf for a few years as well