What helps a lot on modern cars is their use of a coolant-to-oil heat exchanger. It's function is two-fold: It helps warm the oil up faster during engine warm-up, and also helps cool the oil when the oil is at full operating temperature, as long as the radiator works well and keeps the coolant temperature under proper control.
I am not sure if this is as simple as the "higher viscosity is always better thanks to the Stribeck curve" argument.If your oil started at 8Cst, per university 101, your wear would be incredibly higher.
In the early cold stages, it's thick, providing ample oil film thickness. When it's hot, the additives are there...it's the "warmup phase" that the wear occurs, queue Magnatec...
Thought I might modify a few Stribeck curves to demonstrate what happens to engines when running cold, with cold oil. For reference, hydrodynamic lubrication is where a lubricant, the load, and the relative motion produce sufficient separation forces to keep the parts away from each...bobistheoilguy.com
If cavitation was a big thing in everyday passenger vehicles, the journal bearings would be damaged from cavitation errosion. How many times have you heard of or saw erroded/damaged journal bearings talked about or shown here, or anywhere else?I am not sure if this is as simple as the "higher viscosity is always better thanks to the Stribeck curve" argument.
What I am worried about is not the Stribeck curve but things like cavitation and oil starvation at very high viscosity, which are not well-studied. There is a paper, which says that a low-viscosity lubricant does a lot better than a high-viscosity lubricant in reducing cavitation in a sleeve bearing.
I'd love to see an engine teardown from one running 0w-8 or 0w16, babied until the oil reached operating temperature just to play it safe. My bet is as the grade of oil gets bumped up in that application the wear decreases.To add ... motorcycles rev to 11,000+ RPM running 20W-50 all day long, and I never hear of their rod or crankshaft journal bearings being damaged by oil cavitation.
With my plug-in hybrid, idling is out of question. In fact, I don't turn on the ICE (turn off the EV mode) until I pass the first traffic light with the car traveling 20 mph so that I don't waste fuel. Therefore, 0W-16 is the answer, and bring on the 0W-8 for the next-generation Prius Prime!
Recently, a reader criticized a comment I wrote a while ago in which I claimed that it harms your engine if you hoon it while cold. While I stand by the comment, I’ll admit that it was unsatisfying and devoid of detail. So I reached out to a powertrain engineer to help me fill it in a bit.jalopnik.com
Blow by. The pistons displace as much air going down as they do going up.Cool video! When I see that, for some reason I want to use an even thicker oil. lol
What's causing the dust? Is it oil vapor, droplet or mist ... and is it caused by heat or rapid movement?
what's the technical name for it?
Exactly the opposite.after reading this, I want to use only 0W synthetic for when the engine and oil are cold.
The following is from the link provided by Gokan:
"The second problem is that most engines are constructed of aluminum these days which has a much higher coefficient of thermal expansion than the old cast iron structures. Thus, under extremely cold conditions the clearance between some of the key mating parts gets very small.
Of particular concern is main bearing clearance where the main bearing housing (the engine block) is constructed of aluminum and the crankshaft is constructed of steel. Thus, the aluminum housing contracts much more than the shaft and the bearings get extremely tight. The combination of reduced bearing clearance and lack of oil flow is a recipe for metal-to-metal contact and rapidly increased wear. "
If the AL surrounding the bearings " contracts more" that means the bearing clearance would be larger, not smaller.