Just a thought as I am not qualified in any way to comment on oil performance (maybe some here are, I don't know).
When we start out with a cold motor, shifting into first always feels like a jackhammer! Right? My guess is that clutch plates are sticking together somewhat more than a hot motor oil would do. Also we are usually still in high idle mode which makes it worse no doubt.
I think that oil manufacturers formulate their oil intended for automotive use to cling or retain a film to all surfaces to lessen wear effects caused by initial start-up (where most wear occurs). Good so far (at least for dry clutches).
But this same clinging effect will also tend to bridge clutch plates somewhat like a torque converter especially when temps are low and viscosity higher.
It seems logical to guess that the higher the oil viscosity at any given time, the more drag on disengaged clutch plates = notchier shifting.
This can be seen when shifting very quickly as opposed to lazy shifts (quick shifts occur more smoothly because the dogs are still in alignment because the drag from oil/clutch plates has not rotated the primary or drive shaft out of alignment.
So....to summarize this hypothesis, the clingability of auto oils is good for everything BUT wet clutches. Possibly why low viscosity multi-grades MIGHT be a better alternative for engines that use their crankcase oil to also lube their clutch (and tranny to a lesser extent).
A way around all this? Preload the shift lever and shift quickly.
Fretka .
