GM recommends Mobil 1 15w50 for 2016 Corvette

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Originally Posted By: Shannow
To get back to the sump, it runs down the (quite massive) surface are of the valley, which is unlikely to be much over the block coolant temperature.

What's the percentage oil flow to the heads versus the mains and big ends ?

Even if the oil returning from the heads STAYS at 250-260 (it wont), the majority (bigger percentage) will be exiting the mains and big ends at 300F.

The oil from the mains and big ends is straight back to the sump, as opposed to being cooled by the water jackets in the valley....clearly, the heat in the valley having a flow of fresh (cold) coolant between the cylinder and itself CAN'T be 266F head temperature, can it ?

Look at the "percentage flows" (sic), and the temperature rises that occur for those masses, and you can add up what makes a difference with relative ease.


Do the test at 4000 RPM I suggested above, and that will tell you how much more the sump temperature rises when you add a lot more HP and combustion heat that is up and above the heat generated only by the bearings from RPM. I think you will see an even more significant increase in the sump temperature.

When the heads (and also other internal parts in contact with the oil) run hotter due to increased combustion, the cooling system doesn't really keep the heads and cylinder jackets at a constant temperature. The cooling system temperature also rises, and it can be significant, especially if the cooling system is lacking. When you're taking about engines putting out 450 to 600 HP, the heat generated from combustion is huge.

All of that causes the engine mass to run hotter which causes more heat to become absorbed by the oil, All of that is also contributing to raising the sump's temperature, along with the temperature rise in the bearings - it's a multifaceted scenario. That's another reason race cars have crazy coolant systems along with oil coolers. Keeping the sump temperature down as much as possible is a key factor for serious racers who don't want to flatbed their car back home.
 
I could run all day long at 4000 RPM with only a slightly cracked throttle (a very low HP level) to keep the car at a constant speed on a flat road, and the sump temperature would increase some as you have said due to the increase in RPM alone.

But if the engine was at 4000 RPM and towing a large trailer up a steep hill 10 miles long that needed WOT the whole way, the sump temperature is going to rise much higher than when just cruising at a low HP level at 4000 RPM on a flat road. The bearings are turning at 4000 RPM in both cases, but the increased sump temperature between the low HP and high HP levels is now due to the increased heat of combustion and the rising temperature of the engine mass conducting added heat into the oil.
 
Originally Posted By: CapitalTruck
This has been the case for some time. Here's from 2014 manual:
Viscosity Grade
SAE 5W-30 is the best viscosity grade for the vehicle. Do not use other viscosity grade oils such as SAE 10W-30, 10W-40, or 20W-50.
Why the prohibition against 10W-30? I can see that grade being useful in states like California and Arizona, where winters don't exist. Would running 10W-30 really damage the engine?
 
Originally Posted By: veryHeavy
Originally Posted By: CapitalTruck
This has been the case for some time. Here's from 2014 manual:
Viscosity Grade
SAE 5W-30 is the best viscosity grade for the vehicle. Do not use other viscosity grade oils such as SAE 10W-30, 10W-40, or 20W-50.
Why the prohibition against 10W-30? I can see that grade being useful in states like California and Arizona, where winters don't exist. Would running 10W-30 really damage the engine?


I don't know about 10W30, but for quite some time GM didn't want people to use 10W40, because some of the early mineral 10W40's were poorly made with lots of polymer VII's that broken down and caused engine issues. I'm sure something like a full synthetic M1 10W40 would not cause any issues. They write the manual for the lowest common denominator, not a BITOG thread.

My GM manual says to only use 10W30 or 15W40. These have less VIIs than 10W40 or 5W30 in conventional mineral oils. However I have happily run a semi-synthetic 10W40 Euro rated A3/B4 oil without concern. And next I'll probably run a full synthetic 5W30 without concern.

I think the prohibition is against old style VII heavy oils on a conventional full mineral base, not against the viscosity grade as such. Most of this was taken care of when they produced 5W30 to the Dexos standard, which only exist as a full or semi synthetic.
 
Originally Posted By: veryHeavy
Why the prohibition against 10W-30? I can see that grade being useful in states like California and Arizona, where winters don't exist. Would running 10W-30 really damage the engine?

I'm sure it wouldn't, but GM, like many others, wanted to go to one basic viscosity and specification to reduce room for error and to maximize CAFE credits, as another benefit. Realistically, 5w-30 was a sensible recommendation for most, given that the HTHS of an ILSAC 5w-30 is about the same as an ILSAC 10w-30, and the cold cranking is good enough for most of the continent.

One could argue about the shear stability of 10w-30 over 5w-30 back then, but given short OCIs and North American driving habits, it tended to work fine.
 
Originally Posted By: ZeeOSix
I could run all day long at 4000 RPM with only a slightly cracked throttle (a very low HP level) to keep the car at a constant speed on a flat road, and the sump temperature would increase some as you have said due to the increase in RPM alone.

But if the engine was at 4000 RPM and towing a large trailer up a steep hill 10 miles long that needed WOT the whole way, the sump temperature is going to rise much higher than when just cruising at a low HP level at 4000 RPM on a flat road. The bearings are turning at 4000 RPM in both cases, but the increased sump temperature between the low HP and high HP levels is now due to the increased heat of combustion and the rising temperature of the engine mass conducting added heat into the oil.


So I've seen a 40C increase in temperature due to RPM alone (and as I said, slightly more parasitic losses), and you think I'll see a similar increase from load ?

I don't thinks so...

Can't test on that car as no towbar, but the temperature increase due to load isn't going to be 40C.
 
Originally Posted By: G-MAN
Originally Posted By: Nate1979
Manufacturers since the dawn of time has always recommended thicker oil for high load situations (track, towing,mountain driving etc). This is nothing new yet people get surprised at this? Even my lowly 2010 Subaru Forester says this.


Absolutely not true, which was the whole point of my post. For decades, GM owners manuals have had the following wording in them (this is from my 2005 Corvette owners manual). There is no recommendation anywhere to use thicker oil for ANY situation. In fact, as you can see, GM specifically states NOT to use thicker oil.




Maybe not true for GM but true for many many manufactures. What I wrote was absolutely true.
 
Originally Posted By: Shannow
Originally Posted By: ZeeOSix
I could run all day long at 4000 RPM with only a slightly cracked throttle (a very low HP level) to keep the car at a constant speed on a flat road, and the sump temperature would increase some as you have said due to the increase in RPM alone.

But if the engine was at 4000 RPM and towing a large trailer up a steep hill 10 miles long that needed WOT the whole way, the sump temperature is going to rise much higher than when just cruising at a low HP level at 4000 RPM on a flat road. The bearings are turning at 4000 RPM in both cases, but the increased sump temperature between the low HP and high HP levels is now due to the increased heat of combustion and the rising temperature of the engine mass conducting added heat into the oil.


So I've seen a 40C increase in temperature due to RPM alone (and as I said, slightly more parasitic losses), and you think I'll see a similar increase from load ?

I don't thinks so...

Can't test on that car as no towbar, but the temperature increase due to load isn't going to be 40C.


I never said it would be another 40C increase - I'm saying it's going to be pretty significant, not just a few more degrees like you seem to think.

Go find a buddy with a trailer hitch and a trailer you can load up real good, or just someone with a large truck that can haul a lot of weight, and run the testing on that vehicle. Do your same test on flat land to get the sump temperature increase due to RPM increase only like you did with your car. Then load up the trailer or truck with a heavy load and go find the steepest, longest hill you can (not a few hundred feet long, but a few miles at least - like a mountain pass), and do the same test making the engine put out a much higher power level to keep the same RPM.

Compare the sump temperature rise between running at low RPM at low throttle on flat ground with no trailer/load (run 1) vs. running at 4000 RPM on flat ground at low throttle with no trailer/load (run 2) vs. running at 4000 RPM with a very heavy trailer/load (lots of throttle) up a very long and steep hill for an extended amount of time (run 3). You might be surprised that the delta-T of the sump between runs 2 and 3 isn't just a few more degrees C.

If you can't do it, then maybe someone reading this thread might want to try the experiment.
 
Originally Posted By: ZeeOSix
I never said it would be another 40C increase - I'm saying it's going to be pretty significant, not just a few more degrees like you seem to think.


Ahhh, again, we come full circle, you strawmanning me into what you would like for me to be saying and then attacking that.

Secret Agent school taught you many things it seems.
 
Originally Posted By: ZeeOSix
You might be surprised that the delta-T of the sump between runs 2 and 3 isn't just a few more degrees C.


Got an actual feel for the magnitude, or is just like the "equal flow percentage" betting from before ?
 
Originally Posted By: Shannow
Originally Posted By: ZeeOSix
I never said it would be another 40C increase - I'm saying it's going to be pretty significant, not just a few more degrees like you seem to think.


Ahhh, again, we come full circle, you strawmanning me into what you would like for me to be saying and then attacking that.

Secret Agent school taught you many things it seems.


LoL ... you're the one who pulled 40C out of the air ... not me. How much do you think the sump temperature will rise between when the engine is putting out 30 HP at 4000 PRM vs 300 HP at 4000 RPM?
 
Originally Posted By: ZeeOSix
LoL ... you're the one who pulled 40C out of the air ... not me. How much do you think the sump temperature will rise between when the engine is putting out 30 HP at 4000 PRM vs 300 HP at 4000 RPM?


Nope, not pulled out of the air...measured with a type K thermocouple, in my own vehicle...

Why do you say "pulled out of the air ???"
 
Originally Posted By: Shannow
Originally Posted By: ZeeOSix
You might be surprised that the delta-T of the sump between runs 2 and 3 isn't just a few more degrees C.


Got an actual feel for the magnitude, or is just like the "equal flow percentage" betting from before ?


Go do the test and tell us all here. And the flow slit percentage discussion in the other thread was pretty true and I proved it with the very graph you supplied. You just couldn't fully grasp the discussion.
 
OK, here's a comparison of heating rates.

One with constant RPM, and 6 fold load increase, and the other with the same applied torque, and a three fold RPM increase (three times that power).

As you can clearly see, the RPM has a much bigger influence on the power generated in heating the oil than the load (massive fires)....

warmup2.jpg
 
Couple of other pieces from a paper, showing the thermal flows from/to bearings in a running engine, at different RPM....

heat%20flow%20in%20crankshaft.jpg

heat%20flow%20in%20crankshaft%206000%20rpm.jpg


Note the direction of heat flow INTO the block from the bearings.
 
Originally Posted By: Shannow
Originally Posted By: ZeeOSix
LoL ... you're the one who pulled 40C out of the air ... not me. How much do you think the sump temperature will rise between when the engine is putting out 30 HP at 4000 PRM vs 300 HP at 4000 RPM?


Nope, not pulled out of the air...measured with a type K thermocouple, in my own vehicle...

Why do you say "pulled out of the air ???"


Follow along. I'm not talking about the test you did on your car, I'm talking about your thoughts on the additional temperature rise due to high HP levels for extended periods further increasing the sump temperature. You came up with "40 C" for some reason.

Originally Posted By: Shannow
Can't test on that car as no towbar, but the temperature increase due to load isn't going to be 40C.


I never said it would be 40C more ... I said it would be a significant rise, which is more than just a few more degrees C. You come across thinking the temperature rise won't be much more due to the engine putting out 30 HP vs 300 HP at X RPM. Guess it goes along with thinking a PD oil pump doesn't force any additional oil flow through the bearings either.
grin.gif


And to tell you the truth, I have a hard time believing the oil temperature would go up to 135 C (275 F) if cruising down a flat highway at 4000 RPM with minimum load on the engine. If that was the case, then these guys who race their cars on the track for 30+ minutes at a time at much higher sustained RPM than 4000 (like around 5500~6500) would be vaporizing the oil (and bearings) in their engines because the oil temperature would be well over 300 deg F.
 
Originally Posted By: ZeeOSix
Follow along. I'm not talking about the test you did on your car, I'm talking about your thoughts on the additional temperature rise due to high HP levels for extended periods further increasing the sump temperature. You came up with "40 C" for some reason.

Originally Posted By: Shannow
Can't test on that car as no towbar, but the temperature increase due to load isn't going to be 40C.


I never said it would be 40C more ... I said it would be a significant rise, which is more than just a few more degrees C. You come across thinking the temperature rise won't be much more due to the engine putting out 30 HP vs 300 HP at X RPM. Guess it goes along with thinking a PD oil pump doesn't force any additional oil flow through the bearings either.
grin.gif



OK, again, you are describing "my thoughts"...have I ever said (or though, as that's your forte in answering unthought thoughts apparently) that it's "only a couple of degrees" ?

(Hint, no).

I have said that RPM is the dominant factor in oil temperature rise, and have never discounted load as a part factor...it's just not the MAJOR factor.

As to your incredulity, the point at which the type K is situated when I drop it down the dipstick hole is exactly where the full/add zone on my dipstick is...it's right where the oil drains back from the rotating assembly, and prior to it making contact with the sump walls...so it's an accurate reflection of what's going on with the oil exiting the spinny stuff.

HTHS...it's 150C, as that's reflective of bearing temperatures...why the incredulity ?
 
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