The basic idea to use another combustible in additon to the dimethylether is that the the caloric value of ether is rather low. So basically is is possible to run a model diesel on ether and castor oil only but if you want to improve performance it is mecessary to add something more powerful like white spirit or kerosene. Diesels have a lower specific power compared to glow engines so if you want the engine to propel somthing is is better to keep the ether percentage as low as possible.
As far as cleaning is concerned: I have a vast collection of old engines ,most of them stored without proper cleaning after the last run ( yes, shame on me..) and every now and then I pick one and put it in a jar filled with thinner.
This is a powerful solvent and it dissolves all gummed up castor oil without corroding the metal.
Chemical products break up the oil molecules but sometimes also the metal the engine is made of....View attachment 116328
50 years of collecting model engines ( not to mention the loose parts..)