Although some have reported that Apothecary castor works well, my experience was not good.

About a year ago, I mixed up some fuel using castor from Bulk Apothecary and then delayed using it for several weeks. When life settled down enough to resume flying I had forgotten all about the fuel mixing. I went out to the field and immediately had problems. None of my engines would run a whole tank of fuel without dying nor would they idle reliably. I got pretty darn good at deadstick landings though!

I struggled for a month or two trying different things like different glow plugs, tank position, foam around the tank, and different propellers. Finally I remembered that I had mixed the fuel. I drove to a hobby shop 100 miles away and bought a gallon of Omega 10%. Suddenly all of my engines ran perfectly. Now all I use are Klotz oils in my home brew fuels and have not had any problems since.

By the way, I should have known something was wrong with the Apothecary castor because the exhaust did not have that familiar castor smell we all love. It smelled vaguely familiar but not right.

In this hobby it’s often risky to use off the shelf stuff and assume it will work as well as stuff intended for our hobby. Fuel components not intended for internal combustion engines can be a hit or miss experiment. Off the shelf paints can be a gamble as well.