I've use lemon oil. I was told by a guy at a Whole Foods in Atlanta to put a drop or 2 in a liter bottle (or bigger?) I was carrying at the time. You can tell...it goes a long way. It actually feels/tastes too oily either way. Adds a nice freshness other than its other health benefits. Fresh is best, but its so easy. I've been using a little chlorophyll lately, too. Jeanie