My opinion exactly. I'm not sure why folks prefer synthetic over castor.
Some like to use synthetic oil, I'm not one of 'em. Nuff said.
TCraftlover, you asked for some information. Information was supplied. The love or hate for synthetic oil was not in play.
Back in the early '50s I started using Fox Superfuel which contained 29% castor oil and 5% nitro. That worked perfectly for Fox Glow engines and all other engines including Johnson 35 Stunt Supreme, Veco 35, K&B all sizes available, Super Tigre 35s, and even K&B 6.5s. 1/2As needed a little more nitro, yet they liked lots of oil. I keep several Cox.049 1/2 A planes available for kids to enjoy in my back yard. Some always said they needed high nitro! WRONG! They like lots of oil. I have some 20% castor oil fuel with 10% nitro and the .049s run great with that mix, which was left over from Ducted Fan days. Some years ago an engine guru in a magazine revealed that small engine secret and it works.
Now I run with my RC engines usually 10 or 15%nitro and mixed oil because it is available and it works. I do like castor oil but a mix cleans engines better. All castor oil generally will gum up pistons over time. Using some synthetic, 40% or better, will keep the engine cleaner, even the old iron pistons of "yesterday".
So, no hate, no "preference", other than just simply making things a tad easier and neater.
I use Wildcat because I drive through Chicago area each year. Venture Hobby, Dundee Road in Wheeling sells Wildcat much cheaper than local area stores. I pick up a few cases of varying mixes, and get through the year here in the Houston area. I have kids and grandkids in the area and lived there for 17 years myself. Old Home place. The founder of that HS is an old friend so I have to go there. He and I have USAF backgrounds and we each had a couple years time flying the Fairchild C-123, different times different places, but the connection was there.
So castor or syn. Your choice and it all works. Have a nice whatever of your choice!