If some were able to understand the study I presented from 36 years ago ( and other studies) you would know that some experimental 20 grade oils of the time worked just fine. Just as good as thicker oils and for 100,000 miles. And in older engines not specifically designed for thinner oils. The experimenters admitted that their oils were not as good as commercial oils of the time. And now oils are much better and able to withstand fuel dilution otherwise they would likely not recommend 8, 12, or 16 grade oils.
I conclude that oils of today are usable even with grades lower than 20. And that fuel dilution will not occur to the degree nor effect wear as it did as much in the "lesser" 20 grade experimental oils of 36 years ago. Also, even with oil films that many say are near zero the wear is normal in these thin oils. So there must be more to it than a simple value of MOFT that some are weighing in as the main and possibly only factor. Just looking at what we now have to use for motor oils there MUST BE more to it than just MOFT, otherwise none of these oils would work without destroying the motors.
Multiple graphs show that MOFT is less in thinner oils but none show that lesser MOFT = more wear. And there is evidence that these thin oils (with the lease of MOFT values ) are very usable. Billions of miles in millions of cars running 20 grade oils for 25 years just fine, is just not enough evidence of their value for some people.
Ali
From the science and data on the effects of viscosity on MOFT and wear vs HTHS info, I'd say it's a risky move.
