Originally Posted By: Shannow
Originally Posted By: SR5
Not arguing, just asking, shouldn't you take RPM into account, so something like HP/L/RPM
Most of those small engines that make high power are also revving more, so the power per stroke is less.
At what RPM is the peak power for the 'vette, the Honda and the BMW ?
Not quite, and your intuition is pretty close...the comments regarding power output and power density HAVE to be read in terms of cylinder pressures (torque), and RPM (the rate at which you do torque).
A V-8 is certainly torquey, and yes, HP/L wise relatively poor...BUT it can pull like a steam train at very low RPM, something a high revving Honda engine just isn't good at.
Clearly, RPM builds oil film thickness, basic physics.
So a no torque, revvy engine can survive much easier on a thinner oil than a torquey V-8.
Red Herring arguments like "so I need to install 20W50 in my high power density revvy Honda" aren't based on an understanding of the topic.
Fundamentally agree. But this comes back to the basic question...
This says 15w-50 for track and competition events. Not daily driving. It says that plainly. Is that wrong? Will an engine fail early because of that?
A v8 may be able to pull harder, lower, but if that was really the condition of criticality, then this recommendation would be stated plainly in the non-CAFE, over 7600# GVW chevy truck manuals, where there is a much higher chance of long, sustained, high loading on the engine. Is it there?????
Or is it because the corvette's cooling capability for the oil is poor relative to anything else, so the heaview oil is necessary to maintain some adequate film in the bearings?
At the same time, diesels can pull longer, slower, and with much more cylinder pressure, higher low end torque, etc. And they are trending towards lower viscosity lubricants (granted with much larger sumps and better cooling).
While your (notionally valid, what is a standard European design 2.0L engine and how does it relate to the bearings in either a GM performance V8 or other more run of the mill engines????) graphics pop up over and over for good reason, the purpose of the discussion is to ask why this popped up where it did, when it did, and why.
Regarding power and RPM, yes there is a curve that may be more telling, but:
Vette:
http://media.chevrolet.com/media/us/en/chevrolet/vehicles/corvette/2016.tab1.html
455HP @ 6000
460 lb-ft @ 4600
Honda: http://recalls.owners.honda.com/vehicles/information/2015/Accord-Hybrid/specs#mid^CR6F3FEW
141 hp @ 6200
122 lb-ft @ 3500-6000
http://www.vtec.net/articles/article-image?image=1181658/14accordhybriddyno.gif
The electric component skews this one a bit, I know...
BMW:
http://www.edmunds.com/bmw/1-series/2011/road-test-specs/
300 hp @ 5800
300 lb-ft @ 1200 (flat to ~5000 RPM)
Of course we know BMW could and have pushed 60wt oils in some circumstances...
These are just examples to compare because I know them because I own them. Not necessarily end all be all case studies.
But if one is going to argue that the vette driver is going to be thrashing his car around every second of every day, requiring a 15w-50 for driving on surface streets and highways, because otherwise the engine wont be protected is sort of dubious... Especially if this trashing results in decent RPMs in the engine...
