so why can't we just but like 0-5w on the car and just change it sooner that 6000M. i maybe wouldn't go as far as racing spec oil or maybe not even 0-5w, but if we just do the oil change sooner, and take care of the engine we should be able to get more horsepower out of our cars.(less friction = HP)
in regards to the wear and tear of the engine, i agree that if we put lower oil the engine will suffer/stress, but to what extent. i mean you are not driving it like a F1 driver everyday.
in my opinion i thing any oil will work, you just have to be aware of what you are using and use the engine accordingly.( don't turn on the car and blast like a mad man, let it warm up)
and you can actually go to a specialty shop that will create a special oil blend for your climate , application and engine. we always sent our oil on our race cars to get analyzed and we got so much information out of it.
it is really amazing what you can gain or loss from poor oil selection.
well, like always this is just my opinion and, it comes from my experience only...