ARO is ATF (Automatic Transmission Fluid) relabelled, put in a smaller container, and sold for 3x the price. Brilliant idea, actually. I always just sprayed WD-40 down in my engines after running them and never had a problem with the bearings rusting or anything.
All I ever wanted was an honest weeks pay for an honest days work.
Also note that if you run it daily ARO is not really necessary. If you plan to let it sit for a while it is good to empty the tank and run the motor dry, then put ARO or WD40 in it. That is the worst part of nitro for me, all the BS you have to do to it after you play with it. Tuning is not that bad once you have a baseline.