ORIGINAL: Old Sourdough
I respectfully have to disagree with Bud about fuel. If your older .15's were well broken in and well used, and they are of the iron piston/steel liner variety, DO NOT use off the shelf R/C fuel (especially Morgan fuels) in them unless you want to start replacing parts or engines soon! You will clean out the varnish you built up using the all castor fuel and rapidly lose compression and front bushings, especially if you have a slightly lean run or two. You are correct that you should look for a fuel with a large percentage of Castor oil as the lubricant.
Heh I was talking Old Not antique
Old to me is surviving 2 flying seasons without getting a bent shaft or ran to lean. I have never had a problem with any of the Morgan fuels. Granted you older guys ( older being the same people I look to for answers when I have a problem ) may fly engines as old as I am tho. I have never had a failure due to lack of lubrication. Generally everything that has ever failed on me has been me turning the needle in just that lil to far. Or lack of avoiding the ground at high speeds. I was just stating what I run in my engines.
But I would recomend following the recomendation these guys have given you as there wisdom is way past my years. They are the same guys I allways look for answers from when I have a problem as I stated above. I was just stating what I run in my engines.