For several years now, I've been running all my Cox engines on Sig Champion 25% fuel with some extra Klotz castor added to each quart bottle. It's worked well for me but I see that it has been discontinued(Tower's site also shows other popular Sig items as discontinued such as the Four Star series, what a shame.) I have enough fuel to last into next year but will then have to switch to something different. It's tough to change when something works so well for you. Most of the other 25-30% nitro fuels I've seen are low in total oil content or don't have any castor at all in the mix, not to mention more expensive. As the market narrows, I wonder what our 1/2A glow fuel options will be in the near future. Like many of you here, I've got a rather large collection of Cox engines that I want to run well into the future. Lots of 1/2A planes I dream of building and flying. I'm afraid the lack of availability of a suitable fuel may be the largest threat to our segment of the hobby.