boraticus, I think the issue is with the words you use in your post: "necessary" and "required." Those two terms mean different things to different people. "Required," to me, means the minimum ... and I usually aim higher than that.
Now, look at the oil in tpitcher's photo again. Think that stuff is doing nice things circulating through the motor? Wouldn't it be better to get rid of that? Isn't that what oil filters were invented for?
For motors that do not have oil filters I recommend a couple extra flushes when the motor is new to get rid of that stuff. I can't prove that it is "necessary" but common sense tells me it is a good idea if I want the engine to run well for a long, long time. Can I prove it? No, but I don't limit myself to only things I can prove.
So, my advice remains the same. Yes, you may get the exact same service from fewer oil changes, but you can't prove that either.
Now, look at the oil in tpitcher's photo again. Think that stuff is doing nice things circulating through the motor? Wouldn't it be better to get rid of that? Isn't that what oil filters were invented for?
For motors that do not have oil filters I recommend a couple extra flushes when the motor is new to get rid of that stuff. I can't prove that it is "necessary" but common sense tells me it is a good idea if I want the engine to run well for a long, long time. Can I prove it? No, but I don't limit myself to only things I can prove.
So, my advice remains the same. Yes, you may get the exact same service from fewer oil changes, but you can't prove that either.