Mixing oil is definitely a minority opinion. Oil companies do it all of the time to make a semisynthetic, but they prefer to overcharge you for their mix rather than have you experiment with your own mix, and maybe blame them for any bad results.
I agree with Mark Lawrence at his Calsci motorcycle site (a quote is below), after my own testing for shift and clutch feel and oil longevity. Note that I change my unusual mix at least every 3500 miles even though it is a semisynthetic:
"I'm sometimes asked if it's ok to blend your own oils. Yes, it is. Oils are all made out of pretty much the same chemicals, and nothing really bad will happen. If I wanted to blend my own oil, I expect I would use something like 25% Motul 5100 10W-40 and 75% Chevron Delo 15w-40, which would get me both the advantages of a lot of diester stock (5100 is pure diester [I think he meant 7100]) and the diesel additive package. In the winter, however, I would use 25% Motul and 75% Rotella synthetic, to get the superior low temperature performance. In fact, I just run Rotella synthetic in everything I own, year round: ST1300, DL650, Superhawk, Chevy Silverado, motorhome."
Larry constantly attacks any idea he does not agree with.
“Banking institutions have banished precious metals and substituted a more fluctuating and unsafe medium; they have withdrawn capital from useful improvements and employments to nourish idleness for the few, who prefer demoralizing pursuits to labors useful to the whole; the peace of the whole is endangered by evils more easily to be deplored than remedied." by Thomas Jefferson,1810 (edited)