Each and every one of our different vehicles has specific "needs" and requirements that may not match the manual. My F150 ecoboost ABSOLUTELY dilutes the oil with fuel and being in South Florida, does better with a higher viscosity. This is no surprise. What is interesting is that there are plenty of 3.5EB owners with failed timing chains and cam phasers at 100K miles, and they "wonder" how on earth this could happen... Answer, chains last longest with CLEAN 30 viscosity oil. Answer: Ultra thin oil, significantly contaminated with particulates and containing raw fuel or a high percentage of fuel evaporates, simply is not up to the task with some engines. Despite a glowing UOA.
People truly believe that oil can go 10,000 miles or more between changes because the UOA results show the oil to be in good shape and wear metals to be low. Yet they completely ignore the fact that significant fuel gets past the rings, into the oil, evaporates and leaves non-oil contaminates. Ever wonder why some engines seem to use no oil? This can be one reason, the oil consumed is replaced by evaporated fuel components.
With some engines, it's a good idea to choose the right oil and change it frequently. Turbocharged, direct injected engines are often on this list. It should come as no surprise that quick spooling turbo's produce high cylinder pressures from just above idle, direct injection sprays raw fuel into the cylinder, some fuel gets past the low tension piston rings and so on.
And yes, a viscosity increase can effectively offset fuel dilution.