Originally Posted by Spaghetti Bender
With my limited knowledge it seems the 10w40 would run cooler at first; but inevitably the temps will rise, and the thicker oil would provide better protection.
Sounds fair enough to me
I'll take potentially more protection when hot, over maybe less cooling during a warm up phase any day.
Who knows. The thicker oil may even help speed up the warm up period, and that's got to be an advantage
With the true synthetics, cold cranking/pumpability is well known and proven to be superior to mineral oils or their Franken offspring anyway.
Of course there's the issue of film strength.
I'm uncertain that if you could put a dozen experts in a room to debate the matter, a conclusive outcome will emerge.
Especially seeing as once the hydrodynamic state of lubrication has been superseded and transitioned into the boundary state of lubrication, where film strength is no longer relevant. The anti wear additives literally take over anyway as a last line of defence against wear.
On my bikes, I have noted that they're not consuming much in the way of anti wear additives anyway.
So the heat and pressure that's required to activate them is not present.
To my way of thinking the oil I'm using must be doing it's job very well before things get that critical in the hydrodynamic state
So ultimately, there's a lot of reserve additive left in the oil which I'm currently using.
I'm probably throwing away about 85% of what I actually start out with in the fresh oil after 6,000 Kms.
All I know, is that a thicker grade of oil in a particular nominated basestock, will inevitably have more in reserve in terms of hydrodynamic protection when temps rise.
It helps when the manufacturer recommends the thicker grade of oil in the first place. Seeing as they designed the thing anyway.
And they empower me, to make my own mind up by using the table in the owners manual to verify it's suitability for my ambient temps.
The theories about a thinner grade oil in a particular basestock, being able to prevent thermal runaway better than a thicker grade of the same basestock is not conclusive. At all.
There's absolutely no proof yet as far as I know.
I will wait and see.