My friend use before in Honda CT. Seems it won't evaporate (disappear) if revs kept below 3to 4k rpm.
Highway runs then seems to consume some oil.
Another friend in his kelisa use 5w-30 2L mixed with 5w-20 1L......

5w-20 oil??

i agree with the rev range comparison between small and large engine but we cant be sure the heat produced by 3 cylinder 1L at 5k rpm can even match the heat from a 4L having twice the no of cylinders revved to 3k rpm and my gut is telling me that it will be lower in 1L

critically thinking, i think the grade of oil we can use depends more on driving habit and engine normal rev range. all i have to do is to learn how to read and compare different oil specs and see if it protects the engine at my rev range heat, if it does, get the thinnest one for best lubrication. if want to use thinner oil, go with bigger budget, its a calculated risk

i might fork out some money for UOA just to be sure, this result can mean a big change on the rigid classification when recommending oil to others, oil option can be made more flexible by having smarter consumers

thanks for the supporting comment
u have just boosted up my confidence buddy! thanks
no right answer until we try it on and do UOA on the oil. my guess is ok, like mixing used cooking oil and fresh one, both have different viscosity but when heated they mix and come to one final viscosity but then the oil we have in the car now will not have same characteristics of the original spec on neither of the bottles

2 5w30 and 1 5w20, chances are the oil in general would behave like a very light 5w30 but it could be more complex hehe

what about worrying about viscosity being too thin that causes oil pressure loss and losing the capability of keeping the conrod and main bearings in full-float mode via lubrication?

too thin of a viscosity?

low oil pressure is a concern and there is no way i know for sure that its gonna be too low so i referred to sample of uoa reports, judging by what ive seen and ones posted here it should not be a problem.

ive poured in torco 5w20, the viscosity index and tbn number on it is convincing so the oil should be stable. only need to test it and see, its a calculated risk

people told me not to think too much and be dare to try but sometimes they tend to do the same by raising up concerns..thats ironic and confusing :-)