15W40 4T engine oil -unobtainium?

[grumpyunk]

I think, no basis other than being around for a long time, that you would be fine with just about any that do NOT have a 'friction modifier' additive. The listed viscosities available should be adequate for the appropriate temperature range given.
My Honda CB350 recommended plain old 10W30, nothing special except the Sx, spark ignition API rating.
If you have flat tappets or cam followers, I would go with the Rotella/Delvac/brain-fade for RPM DELO - came to me. Any of the CD rated have a bit more ZDDP as I understand, which helps the flat tappet/cam follower handle the sliding friction better, and extends their life. I think.
I have two or three varieties of diesel rated. I am currently using the WalMart Super Tech 10W40 diesel rated lube. No synthetic, just plain old natural.
The CB350 didn't care one way or another, and depending on your engine design, OHC or OHV, they should be good. The CG250 is a simple design that doesn't seem to care from all I have read. Not sure what engine is being discussed.
tom,

[culcune]

Originally Posted by grumpyunk

The CG250 is a simple design that doesn't seem to care from all I have read. Not sure what engine is being discussed.
tom,

The posters bike is a bike we used to have years ago in the US. It uses a clone of the engine found in the TW200. Pretty much the exact clone. So, like the SSR XF250 (clone of the Suzuki TU250 but uses a carb), these bikes buck the trend of using the common Honda-clone-ish engines most all Chinese dual-sports generally use.