Originally Posted By: Shannow
Originally Posted By: JHZR2
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?
What sort of a strawman is that ?
No, it clearly indicates that track temperatures are higher...and recommends a higher viscosity in those circumstances, which provide a greater viscosity reserve.
How does that get turned around to engines failing early in daily driving ?
I didn't say that, nor did GM.
I didnt say you did. In fact, I said about daily driving before you even posted anything here. Id recommend some review of the string of commentary and not take things as an attack on you. The discussion was based upon my argument that rather pedestrian engines making about the same HP/L last a very long time in regular use. That stems back to the earlier comments that most 'vette drivers slam on their cars, which I disagree is a valid reason to up viscosity in non-track circumstances (which is why 30wt is recommended per the manual for normal circumstances).
Originally Posted By: Shannow
Originally Posted By: JHZR2
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?
Looking at the frontal area of a truck versus a Corvette, clearly they have different design points, don't they ?
What size radiator and fan do Chev install on the towing pack for the Corvette ?
Thanks for validating my claims that the viscosity recommendation is based upon poor cooling and not WOT slamming on the throttle at stoplights and around town, which a towing rig would notionally do quite often in mountain driving or other such things, and for which the >7600 GVW variants dont have CAFE to worry about... Thus they could have had the 15w-50 requirement for all time...
Originally Posted By: Shannow
Originally Posted By: JHZR2
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).
Yep, as per previous, I'm not sure what the cooling system and sump size is in the diesel Corvette tractors, but would assume that it's pretty big...and the "thinner oils" that they are speccing for the diesels still have an HTHS of 3.5+.
Agreed. Point I was trying to make is that even torquier, slower engines can be designed to operate under severe service, low speed, high torque operations with ever-less-viscous oils. Since there is a cross section of oil specs getting more robust (including Dexos), and oil viscosities dropping across the board, it doesnt make the vette v8, low speed high torque situation seem all that out of the ordinary. Other than some front end cooling capacity limitations, I find it dubious that the situation of design or stress in the vette engine, even the Z06, is that much worse than anything else.
Originally Posted By: Shannow
Originally Posted By: JHZR2
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.
Sorry, it was the only chart that I had at my disposal when I was answering SR5's question, having neither the Corvette details nor your Honda/BMW details, when the strawman was presented...
Concur, but I recommend you re-read the posts. We were getting to a discussion along the lines of that a 4 cyl is easier/harder on the oil. If oil squeezes out of the bearings easier in a V8 given its output, torque curve, and power/cyl, then the bearing spec and sizing to accommodate the load should be adjusted accordingly.
Originally Posted By: Shannow
Originally Posted By: JHZR2
My Honda Accord Hybrid puts out 70.5 HP/L... Should I run M1 15w-50 in it when Im going to be driving fast/hard on the interstate???
My 135i puts out 100 HP/L. It requires an LL-01 oil. It also has known high oil temperatures. Should I take that up to a 50wt for driving fast from stop light to stop light?
While you have a point comparing apples and apples, you have introduced OTR transports, same engine in trucks to the conversation, then attacked (lightly) the fact that a Euro 2.0 isn't the "same" as the engine in question...
So in order to have something "real", I'll drop back to basic bearing design curves...
L/D of 1/4 is close to most automotive designs, and clearly, exactly the same relationships hold.
More RPM, more MOFT, More RPM, for the same MOFT, you can increase the load or reduce the viscosity. For lower RPM, more load, you can get the same MOFT by increasing the viscosity.
Basic science, applicable to bearings, and not specifically the Euro engine in the pic I linked to.
BTW, Honda papers on their quest for lower overall friction have stated that they are now increasing bearing dimensions (diameter and length) while reducing radial clearances....look at the above chart, and you can see what direction they are trying to go with MOFT.
And yet another reason why "so I should run my Honda on 15W50" is a strawman when talking
specifically about Corvetter engines, which you have corrected me on.
Violent agreement of the "knobs" of which a designer can turn. From there, its all about margin. You know as well as anyone that margin is designed in, there is a practical limit on the design, SWAP, cost, efficiency/losses, and there is risk to be accounted for.
Again, the point of mentioning Honda or anything was to bring forward the point that the power density based upon displacement is not particularly high or advanced compared to much more benign cars. Yes, V8, more power per cylinder, but then per the chart and discussion above, you know the way the designers should go too... And they know their design parameters, which affect margin when using a 30wt oil even at high oil temperatures.
Is the bearing design in the 6.2L Vette engine different from the 6.2 truck? Practically speaking even if a driver is blowing away from stoplights hard, does it matter?
Originally Posted By: Shannow
Originally Posted By: JHZR2
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...
I'd like you to quote where I have suggested or argued that...ties in exactly with the "premature wear" on a daily driver...which I never said.
Again, please re-read the overall discussion and stop thinking that everything is an attack on you or putting words into your mouth - it certainly is not my intent. The comments on vette daily drivers thrashing their cars from every light (as a generic roll-up of some of the prior discussion), and the use of that as an excuse to run 15w-50 was what I was getting at... e.g.:
Originally Posted By: aquariuscsm
Heck,owning a Corvette would mean competitive driving anytime you drive it haha. I couldn't imagine putting around town like a lil old lady in one. I'd never run a CAFE oil in a high power muscle car. I'd run the 50wt rec all the time,plus M1 15W50 is dirt cheap. This just goes to further prove that thin oils are for CAFE ONLY and thicker does protect better,or else it'd say "For track or competitive driving,use Mobil 1 0W20".
