1911
If a thick oil requires more energy to flow the rpm drops, therefore the thin oil flows faster. This is most noticeable at cranking limits.
Mobil recommend on my type of car dropping from 20W to 15W at 0c
What are the reasons for this recommendation?
Easier to crank/pump (not at absolute limit)
Flow to bearings
Flow to Cam
Flow to Cylinder walls
Flow as tighter bearing clearance
Perhaps all or none of the above
Even above 0c the thinner oil obtains pressure quicker and less oil bypasses the engine.
I understand 0W oils are more expensive to produce but M1 OW40 (probably now surpassed by CG0W30) is the usual standard fill for European high performance cars, yet they are mostly not used in cold temperature extremes. However in summer a 15W40 would not be an issue for cold starts but why change from a 0W.
However, engine warm up speed and esters/aw additives may achieve more than flow.
For g forces baffles and dry sumps help avoid oil starvation. In the UK with traffic lights, roundabouts, and overtaking opportunities hard acceleration can be the norm, perhaps a reason for a 40 vis still being recommended.
My assumption is that a Cold or dry start is only when drainback has left insufficient oil to protect the surfaces. This would not be the case with a Hybrid constant start situation.
If a thick oil requires more energy to flow the rpm drops, therefore the thin oil flows faster. This is most noticeable at cranking limits.
Mobil recommend on my type of car dropping from 20W to 15W at 0c
What are the reasons for this recommendation?
Easier to crank/pump (not at absolute limit)
Flow to bearings
Flow to Cam
Flow to Cylinder walls
Flow as tighter bearing clearance
Perhaps all or none of the above
Even above 0c the thinner oil obtains pressure quicker and less oil bypasses the engine.
I understand 0W oils are more expensive to produce but M1 OW40 (probably now surpassed by CG0W30) is the usual standard fill for European high performance cars, yet they are mostly not used in cold temperature extremes. However in summer a 15W40 would not be an issue for cold starts but why change from a 0W.
However, engine warm up speed and esters/aw additives may achieve more than flow.
For g forces baffles and dry sumps help avoid oil starvation. In the UK with traffic lights, roundabouts, and overtaking opportunities hard acceleration can be the norm, perhaps a reason for a 40 vis still being recommended.
My assumption is that a Cold or dry start is only when drainback has left insufficient oil to protect the surfaces. This would not be the case with a Hybrid constant start situation.