Hi gents,
just received my new 4RT some days ago here in Italy, and I also got a spare liter of engine oil (I asked for it).
It has two "brand lables" on it, HM moto (the Italian Montesa importer)and MYTOIL RACING(that should be the producer of the oil, but I've never heard of it). Interesting stuff is that is labelled as "special trial 4 stroke engine", "less friction anti wear additives", "Motor oil synthetic high performance special 4T Trial", "Recommended for Montesa Cota 4RT" and it has also all the quantities needed for the 4RT on the box! (0.41 or 0.44 liter depending on filter changing or not).
It's a 10w40r (what's the meaning of the last r? maybe racing!), API CG4/SJ, ACEA A3/E3/B3/B4, PSA-PCDO-PCMO, MB-228.3
Main writings are in English, Italian, Spanish and Japanese, so difficult to say where it's really produced.
Looks like better than the recommended Repsol 4t or Honda Ultra S9, at least on papers.
Have no idea if available in UK and US. Hope this would help.
cheers