The thing with Castor oil is ,that it is cheap insurance, for those times, when things go wrong.It`s a personal choice.I won`t run an engine, without at least some castor in it. Usually, I like at least a 20% total oil content, and 50% ,of that amount ,being castor..Here`s a chart of some testing I did, with varying amounts of head shims ,Nitro,and ,prop sizes..The test engine is a New Norvel BigMig 0.061" with only 2 ounces of fuel, through it ,for the initial break in..With the Break-in ,and, the testing shown on the chart, I`ve only ran a total of 10 ounces of fuel through it since New..I`ve not run the engine since.The fuel, with the least ,amount of Castor, was the Morgan Omega Fuel..If you look at the Chart you`ll see some pretty high RPMs shown there 20,000 Rpm+ ,and naturally, the higher the Revs, the Higher the Temps.I had no way to measure the heat generated, but wish I did..I`m curious to know those numbers too.I`m not trying to tell you guy`s what to do, except that Castor oil will protect, and lubricate your engine,at temperatures, that the Synthetic oil will not..It`s up to you ,to decide if it`s more important, to have a clean plane ,Or ,a well protected engine, in a Oily plane.Unexpected things happen,and parts, for the Norvel engine are getting hard to get , around here in North America. What is the Availability ,of the Norvel engines and their parts like in your Countrys? are they easy to get ahold of? ... Dave