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^ ... "75% of engine wear occurs during cold starts"
... yes, with this endlessly repeated "fact" being specific to cylinder wear given cold-start condensation of the fuel charge washes off the oil film protection no matter the oil viscosity.
Ah, good point...hadn't thought to check if the GX has this engine. So then he was off on this point, but that really doesn't address the issue of engine wear with 0W20, which was his main point.
IN terms of cold starts/engine wear, there are tons of SAE studies showing that cold starts are a large contributor to engine wear....I don't know exact percentage of wear it tallies up to, but they all say it is definitely a top contributor to it, but here's one: https://www.sae.org/papers/cold-star...engines-850215
Rapid engine wear is one of the most serious problems associated in the commercial exploitation of carburetter, straight methanol spark ignited engines. The existing lubricants are reported to be deficient in the control of cylinder bore and piston ring wear. Whereas, extensive efforts have been made to develop improved lubricants, the problem of increased wear of methanol has not, as yet, been satisfactorily addressed. The various mechanisms proposed for this increased wear have been examined in this paper. It was recognized that the conditions which aggravate the wear of methanol engines are encountered during cold start and warm-up due to the differences in the volatility characteristics of this fuel.
In this study, cold start wear tests were conducted in a cold room with temperature control ranging from +25°C to −40°C. Wear data of methanol engines, under starting conditions typical of the Canadian environment, are compared with data of a gasoline counterpart. The analysis of these data so obtained suggests that a temperature dependent theory is valid to explain the cold start wear results. Further, the cold start wear can be a significant portion of the total wear and is attributed to the direct attack of methanol on the cylinder walls in the first few seconds of engine operation.
A radiotracer method was developed to measure real-time wear rates of piston rings and cylinder bores in spark-ignition engines. Initial work determined baseline wear rates during break-in and steady-state operating conditions. This work examines the effects of lubricant properties on wear rates of the ring/bore interface. Results show that engine oil service classification, the level of antiwear additives, severe engine aging, synthetic formulations, and viscosity classification have little or no impact on wear rates. These results suggest that concerns of wear between the rings and cylinder bore may not be a roadblock to extended oil-change intervals. Engine operation under cold temperatures appears to be a very important factor in ring/bore wear.
So yes, they don't (at least in the abstract; I'm not gonna shell out $100 or whatever to see if they give a percentage ) . But it's definitely a major contributor, according to their studies. One more reason in my view to use a thinner oil, if it doesn't cause any additional wear under normal operating conditions.
And speaking of this: one thing I have been unable to find is any SAE paper showing that 0W20 produces increased engine wear under any normal operating conditions. In fact, searches I ran with google, ChatGPT etc, and others tend to state quite the opposite. Would love it if someone could provide some actual SAE studies showing this as I'm an Engineer by trade and for me data is king, and I mean wear data specifically. Don't need bombardment with viscosity and the properties thereof, unless it's accompanied by proof showing that this particular grade causes increased wear to my engine, of which I've been able to find precisely zero documentation. But I have seen plenty of opinions on web forums expressing it is so, none of which cite any papers showing it to be so. Even in the Toyota charts shown of other viscosities available, they all show that any of these grades are safe up to 100C which is an operating temperature I've never seen even on my Z06 which has over 2x the horsepower of this engine, even under shall we say very spirited driving.
To study the mechanism of the effect of low-viscosity oils on engine friction loss reduction so as to improve the vehicle fuel economy of the Worldwide harmonized Light vehicles Test Cycle (WLTC) by upgrading the Society of Automotive Engineers (SAE) viscosity grade of the factory fill oil from 5W30 to 0W20, eight 0W20 oil samples were blended with different doses of base oil, viscosity modifier (VM), and friction modifier (FM).
Theoretical analysis by AVL-EXCITE simulation of the key friction pairs combined with practical engine friction torque test and vehicle WLTC fuel consumption tests were carried out. The results showed that 0W20 oils can effectively reduce the engine friction torque by 5.64 Nm and the friction loss by 11.95% with the throttle fully opened; while with the throttle closed, the friction torque decreased by 3.53 Nm and the friction loss by 11.26%, resulting to the improvement of the vehicle WLTC fuel economy by 2.08%. Without deteriorating the durability of the engine, the application of 0W20 engine oil can help to achieve carbon dioxide (CO2) emission reduction and the Corporate Average Fuel Consumption (CAFC) score accumulation.
Low viscosity plays a leading role in the WLTC low-speed and medium-speed segments, while VMs and FMs contribute more in the high-speed and extra high-speed segments, indicating that the oil viscosity is not the only key factor to reduce engine friction. The coordination of the whole oil formulation, low viscosity combined with different additives, is the key to reduce friction loss and achieve fuel economy.
So if SAE studied this and came to the conclusion that I'll spend less money on gas, without harming the durability of the engine....well, kind of doubtful I'll be switching from recommended. On this I think CCG's reasoning is sound.
UOA isn’t really isn’t valid for comparing wear rates due to its particle size limitations, it’s good for observing trends but pretty poor at comparing the wear control of different oils.
The valid data you seek really requires engine tear downs.
Yes, it's a good reference source if you give it good prompts, but not infallible. But what is better? Google? .
Also, not sure why you posted the data about higher temp, the very first post I made in the thread contained the exact same thing, my argument was not about this point but about the general ******** of 0W20 without any data showing it's any worse under normal conditions than 5W30.
Startup Protection: Approximately 75% of engine wear occurs during cold starts. 0W oils are designed to flow faster at low temperatures, reaching critical components up to 40% faster than 5W oils in cold conditions. This rapid lubrication reduces metal-on-metal friction during the first seconds of operation.
Operating Temperature Stability: Once an engine reaches its normal operating temperature (typically 100°C), both 0W-20 and 5W-20 oils behave identically as "20-weight" oils. They provide the same film strength and protection during normal driving.
High-Temperature Caveats: Some specialized tests suggest that under extreme heat or heavy towing, a thicker oil (like 5W-30) may maintain a 50% thicker oil film than 0W-20, potentially reducing wear by 22% in severe service conditions. However, this compares a 20-weight oil to a 30-weight oil, rather than 0W vs. 5W of the same operating weight.
Regarding teardowns and wear measurements, the ASE studies I mentioned did purport to measure wear, fwiw.
Last edited by Pearl22GX; Mar 2, 2026 at 06:05 PM.
... AI search ... no thanks ... artificial, yes ... intelligent, no ... simply turbocharges assembling the most prevalent / repeated "information" floating around in the ether ... great tool but requires knowledge based filtering. In today's world where repeating something 3 times makes it true ...
... AI search ... no thanks ... artificial, yes ... intelligent, no ... simply turbocharges assembling the most prevalent / repeated "information" floating around in the ether ... great tool but requires knowledge based filtering. In today's world where repeating something 3 times makes it true ...
Actually if you understand how to use it correctly, and tell it to take its time (which triggers a more exhaustive search) and to give you references for what it’s telling you, you can cross check what it’s telling you and where it got it from. Which is also true for Google or any other online reference… caveat emptor is the operative phrase, although strictly speaking it’s free, at least for now.
If on the other hand you just take whatever it’s telling you and think it is true, you’re what’s called a PT Barnum person. 😁 Sort of like if you take unsubstantiated claims on the Internet as truthful without checking them out first… trust sparingly, but verify strongly, is the only way to fly on the Internet. I’ve caught ChatGPT, and particularly Google’s Gemini, in dozens of errors. Even when it gives me sources, sometimes it quotes them incorrectly, so I always read them first.
So yeah, all this talk about it replacing humans in short term, meh…
Last edited by Pearl22GX; Mar 2, 2026 at 09:05 PM.
... AI search ... no thanks ... artificial, yes ... intelligent, no ... simply turbocharges assembling the most prevalent / repeated "information" floating around in the ether ... great tool but requires knowledge based filtering. In today's world where repeating something 3 times makes it true ...
Agreed, it's also easily thrown by prompts.
When ask a leading question and it tends to follow the lead.
So if SAE studied this and came to the conclusion that I'll spend less money on gas, without harming the durability of the engine....well, kind of doubtful I'll be switching from recommended. On this I think CCG's reasoning is sound.
https://www.sae.org/papers/engine-oi...results-922342 - This paper includes 20 weight oils with HTHS viscosities that approach GF-6/7 5W-30s, so even though all oils are 20 weights relevance to the ILSAC 0W-20 / 5W-30 debate exists.
http://www.sae.org/technical/papers/872128 - "Engine wear tests were conducted, using two different engine designs, with single and multigrade engine oils. In one engine there was a significant reduction in bearing wear when multigrade oils were used. For the other engine there was evidence of less bearing wear when multigrade oils were used"
http://www.sae.org/technical/papers/980702 - "Properties of engine bearings were investigated with different bearing materials and different HTHS viscosity oils by means of both an engine test and a rig test.
The rig test well simulated the bearing wear which occurred in the engine test. Lead-bronze bearings with lead-tin-indium overlay gave the least amount of wear in operating under high-speed and heavy-load conditions even with low HTHS viscosi Aluminum bearings without overlay gave good wear resistance in the case of no seizure occurrence. The wear amount of bearings were well correlated with HTHS viscosity, not with kinematic viscosity."
Just to chime in again, the numbers on oil are not weights, but grades; the first (ie 0w) is a winter grade while the second (ie 40) is the SAE grade.
The Winter grade is determined by the oil's ability to meet the performance requirements of two tests:
1. CCS - Cold Cranking Simulator - This is designed to simulate the impact on the speed at which the engine can be turned over by the starter
2. MRV - Mini Rotary Viscometer - This is designed to simulate the oil's ability to make its way up the pick-up tube and be pumped
The limits for CCS are much lower than for MRV, so it is typically CCS that the oil fails, which then determines the Winter grade of the lubricant. So, for example, if an oil tested at 6,200cP at -30C, looking at SAE J300, we know it would not meet the performance requirements of the 0W-xx Winter designation, but we can see that it's below the limit of 6,600cP for the 5W-xx Winter designation, so the oil would be labelled as a 5W-xx.
The SAE Grade
The SAE grade is determined by the oil's viscosity at 100C and its HTHS viscosity at 150C. HTHS is only really a factor in grades where there is overlap, like 8, 12, 16 and 20.
I’ve been reading through this "oil war" and wanted to throw my 2 cents in, and my personal take based on the weather where i live is that I wouldn’t move away from the 0w rating ( I use Motul 8100 Eco-lite 100% Sythetic)
My logic is that the absolute worst part of an engine's life and where the most damage is taken is at cold startup. The 0W is what protects those critical components in those first few seconds before the oil is fully flowing. Even if you don’t live in the Arctic, a 0W reaches the top of the engine significantly faster than a 5W or 10W, and in a V8 with this much complexity, I want that lubrication immediately.
That said, I totally get what ASE and BenCSVT are saying about the operating weight (the second number) when it comes to towing or extreme heat. If I were in the Southwest towing a heavy trailer, I’d probably meet in the middle with a 0W-30 or 0W-40. That way, you keep the superior cold-start protection of the 0W that I value so much, but you still get the thicker oil film (MOFT) at operating temp to protect the bearings under load.
It seems like the 0W-40 is the "best of both worlds" if you want to follow the non-US manual's advice for heavy duty while still protecting the engine during the most vulnerable part of its cycle.
Last edited by guzzy92fs; Mar 4, 2026 at 01:19 PM.
I’ve been reading through this "oil war" and wanted to throw my 2 cents in, and my personal take based on the weather where i live is that I wouldn’t move away from the 0w rating ( I use Motul 8100 Eco-lite 100% Sythetic)
My logic is that the absolute worst part of an engine's life and where the most damage is taken is at cold startup. The 0W is what protects those critical components in those first few seconds before the oil is fully flowing. Even if you don’t live in the Arctic, a 0W reaches the top of the engine significantly faster than a 5W or 10W, and in a V8 with this much complexity, I want that lubrication immediately.
That said, I totally get what ASE and BenCSVT are saying about the operating weight (the second number) when it comes to towing or extreme heat. If I were in the Southwest towing a heavy trailer, I’d probably meet in the middle with a 0W-30 or 0W-40. That way, you keep the superior cold-start protection of the 0W that I value so much, but you still get the thicker oil film (MOFT) at operating temp to protect the bearings under load.
It seems like the 0W-40 is the "best of both worlds" if you want to follow the non-US manual's advice for heavy duty while still protecting the engine during the most vulnerable part of its cycle.
... best approach ... maintain 0w for cold start protection, and go 30w or 40w for operating temperature based on climate and duty loading.
Even if you don’t live in the Arctic, a 0W reaches the top of the engine significantly faster than a 5W or 10W, and in a V8 with this much complexity, I want that lubrication immediately.
If you’re approaching the pumpability limits of the oil, absolutely.
In moderate climates, say above 0 degrees F for example, there is really no meaningful/measurable difference in the time the oil takes to reach the valve-train in an already primed engine with a positive displacement oil pump, which the gerotor pumps in the UR V8s are.
0W oils usually (not always) come with some drawbacks if their own.
0W are usually formulated with thinner base oils (see my first link in my most recent post above regarding chain wear) and rely on more polymeric thickeners to achieve the higher operational viscosity.
This usually (not always) results in a slighter lower HTHS and makes them more prone both temporary and permanent mechanical shear.
Oils, like most things, are a series of compromises and there’s rarely a free lunch.
I honestly don’t see any tangible benefit to running a 0W oil in majority of the southern half of the US.
If you’re approaching the pumpability limits of the oil, absolutely.
In moderate climates, say above 0 degrees F for example, there is really no meaningful/measurable difference in the time the oil takes to reach the valve-train in an already primed engine with a positive displacement oil pump, which the gerotor pumps in the UR V8s are.
0W oils usually (not always) come with some drawbacks if their own.
0W are usually formulated with thinner base oils (see my first link in my most recent post above regarding chain wear) and rely on more polymeric thickeners to achieve the higher operational viscosity.
This usually (not always) results in a slighter lower HTHS and makes them more prone both temporary and permanent mechanical shear.
Oils, like most things, are a series of compromises and there’s rarely a free lunch.
I honestly don’t see any tangible benefit to running a 0W oil in majority of the southern half of the US.
I see your point, Ben, about the compromise of 0W oils and the potential for shear in the long run. But since, at least me, changing my oil every 4k–5k miles max, does that shear even have time to become a factor? I feel like I’m draining the oil long before those polymers have a chance to break down. For me, I’d rather take the 'guaranteed' better flow on every single morning start and just swap the oil out before it has a chance to lose its operational thickness.
I see your point, Ben, about the compromise of 0W oils and the potential for shear in the long run. But since, at least me, changing my oil every 4k–5k miles max, does that shear even have time to become a factor? I feel like I’m draining the oil long before those polymers have a chance to break down. For me, I’d rather take the 'guaranteed' better flow on every single morning start and just swap the oil out before it has a chance to lose its operational thickness.
0W oils will virtually always get formulated with a thinner base oil and rely on a larger does of viscosity index improvers/polymer to achieve the desired operational viscosity versus a 5W / 10W oil
) . But it's definitely a major contributor, according to their studies. One more reason in my view to use a thinner oil, if it doesn't cause any additional wear under normal operating conditions. 
