As an aside I am struggling how one considers one brand "better" than another or even acceptable without an in-depth analysis of what the base stock is, the critical performance criteria, and what the additives are. If this information is not readily available, I would simply buy a brand that is forthcoming with this critical information.
Having said that:
Most motorcycles, unlike cars, have a wet clutch, so besides the what oil is "better" discussion, it also behooves one to consider what oil will not destroy my clutch. Combine the water cooled bike lower viscosity oils with a formulation that includes additional quantities of molybdenum-based friction modifiers and you get the new Energy-Conserving GF-5 / SN designation shown in the API Service label on the back of the container.
Dino or synthetic, I would be very reticent in using any brand of car oil with the latest GF-5/SN spec in a bike with a wet clutch.
Our saving grace is that diesel oil or automobile-specific heavier weights like Mobil 1 - 15W/50 do not carry this GF-5/SN designation because of its higher viscosity. A higher viscosity oil's resistance to flow, is the reason why automobile-specific oils that are not energy conserving have been used successfully in wet-clutch motorcycles without slippage problems.
Key to the clutch issue is the question of friction modifiers. The real issue is to avoid getting the friction so low, with very thin oils containing extra amounts of friction modifiers, (usually high Moly levels) that clutches will slip under normal use.
Exxon-Mobil claims, that the formulation of motorcycle-specific Mobil 1 has none (??) of the friction modifiers that could lead to clutch slippage in some wet-clutch motorcycles. A moot point as we cannot get M1 bike oil in Thailand, however most if not all "bike oil" manufacturers make similar statements.
This is supposed to be the current compelling reason to avoid some automobile-specific formulations that now contain friction modifiers to meet fuel economy mandates, when previously they did not. Wet-clutch slippage can be a problem, and seen more often when you use the lower viscosity oils that are designated "Energy-Conserving" on the bottle.
In reality, all oils have friction modifiers - that's how oil does its slippery, oily, work.
ZDDP (Zinc Dialkyldithiophosphate), has been the chief anti-wear, extreme pressure, and anti-oxidant additive for decades. It is so effective and low cost that it is virtually irreplaceable, which is why it survives all efforts to remove phosphorus (Ph) from oils to protect the catalytic converter.
With modern oils putting caps on the maximum Ph allowed, other additives are now being used to supplement this old standard, such as molybdenum anti-wear compounds and ashless anti-oxidants.
It is your bike and use what you like.
I believe that the best oil, and best available filter, (I like Purolator Pure 1 filters) is cheap insurance. In Thailand I buy fully synthetic Mobil 1 Delvac, or Mobil 1 Turbo Diesel Pickup oil as it has the highest ZDDP concentration of all the Mobil synthetics, and readily available at Mobil Dealers locally or if on the road at many Esso stations. Just try buying some esoteric "bike" oil on the road
In Canada I run Mobil 1 - 15W/50 due to an even higher level of ZDDP than the diesel oils and exemption from the new API spec. Unfortunately, like M1 bike oil, I have not seen this in Thailand
Be aware of the detrimental effect of high ZDDP levels if you have a CAT on your bike or even care if it is degraded by ZDDP
Synthetic oils typically have a greater viscosity index (VI) or the ability to retain viscosity over varying temperature ranges) over Dino oils. The VI degrades over time, so change your oil often, or top up regularly , or you will tend toward wet-clutch slippage no matter what type of oil you use.
