Originally Posted By: Shannow
Re Joe's posts, and looking at Honda RandD Paper 22-2_22e (available
https://www.hondarandd.jp )
"Effects of Low-viscosity Engine Oil on Fuel Economy and Wear"
Originally Posted By: SonofJoe
An oil similar to TGMO with all the same faults & more...
This is a Japanese oil that focuses on fuel economy over all other considerations. I would expect this to contain a high Moly treat. It looks like it's using PMA VII (very high VI, very low KV40 plus low Pour Point). It's worth pointing out that the low-end CCS-35 puts this oil halfway to being a -5W20 (not that there is such a thing).
Per the paper (2010), they are claiming that their brand was the lowest operation viscosity on the market, and that they were working within the 0W20 grade (lowest on J300), using PMA to intentionally make the oil "non Newtonian", and effectively shear under high shear conditions. They use the HTHS100 as a measure.
So you are quite correct, they are using VI, to keep the viscosity low, and the polymer treat rate to make the oil shear in service (temporary) to effectively lower the viscosity in the bearings/skirts etc.
Originally Posted By: SonofJoe
The Sustina 0W20 has a quoted Noack of 13% (so possibly as high as 13.45%). I haven't checked but I would have thought that some of the commoner US 0W20s (something like Mobil 1 which presumably contains some PAO and not based on PMA) would have a lower Noack (around 10%-ish?). As such it would have a lower propensity to lay down piston deposits.
Volatility is one of the mentioned downsides, which is pretty obvious. Others were reduction in controlability of things like VVT actuators with the lower resulting oil pressure, and bearing distress under low speed high load conditions (decresing MOFT, increasing film pressures, and leading to wear and bearing surface fatiguing)
Shannow,
I had a good peruse of the Honda R&D paper this morning (thanks for PM'ing it to me).
It's an interesting read. Part of me applauds its thinking because they are refocussing the oil towards 'daily use' rather than extremes that so many modern oils seem to pander to. They set 'normal' oil temperature at 80°C (I might have guessed higher but who am I to question Honda!) and interestingly set 'hot', not at 150°C (ie standard HTHS conditions) but 130°C (which I do agree with).
Like a lot of Japanese papers, the quality of the work is great but only in answering the specific questions they ask. The questions that could & should reasonably be asked, but AREN'T, are not addressed at all. As such the conclusions they draw are IMO a bit flaky.
Take the use of PMA VII for example. PMAs, despite their fundamental inefficiency, do indeed confer great VI to an oil and yes, their temporary shear qualities in bearings at 'normal' temperatures can be exploited to improve fuel economy. However there's a problem. A Group III, tight narrow cross-grade (like a 0W20 or 0W16) isn't going to contain that much VII and a lot of PMA is critical to making the FE trick work. So to make room for a decent amount of PMA in the oil, you artificially drop the CCS until the oil's half way to being a -5W20 (or -5W16). Of course the use of a thinner base oil mix results in the oil's Noack going up. Now here's the rub. You would traditionally lower the Noack of the oil by substituting some PAO for Group III. However in this case, swapping in PAO would reduce the amount of PMA VII. So you're boxed into a corner where to make the trick work, you're perpetually stuck with a high Noack oil and a stupidly high amount of neat PMA rubber in the oil.
And there's something else I might ask. How normal is a 'normal' oil temperature of 80°C? Does it naturally 'float' to this level or do you only get this by setting your coolant thermostat on the low side? If it's the latter (and I think it might be) how does your engine cope with getting rid of gasoline that condenses in your oil? If your oil never gets hot enough to purge the oil of fuel dilution, then with such thin oils, you might end up in a whole heap of trouble!
