There is no "real" answer to your question unfortunately.

The castor/synth debate has raised the blood pressure of many people on this, and other
forums related to r/c.

Castor has unparalleled performance at high temperatures. When synthetics have burned
away....castor is still there..lubricating.

But....castor will leave a residue that in time,will carbonize and need to be removed.

Synthethics run clean. There is little, if any residue left over and the lack of residue is
IMO sometimes interpreted as "better".

The fact that it "vanishes" without a trace should bother you.

Fuel manufacturers have a vested interest in convincing you that their "special" oil is better.

Truth is...if it's so "special"...why doesn't the whole world use it?

Dirty or not. Castor stays while the others burn away.

My philosophy is simple. It's cheaper to remove residue than it is to replace metal. Your 4C engine
represents a sizeable investment. Better to take care of it.

I'd suggest a fuel that contains at least SOME castor if you intend to keep your engine for
any length of time. Fuels such as Powermaster, Omega, etc...have ample oil/castor content
to keep your motor running well for a long time.

Hope this helps.

'Race