ML Dude,

Over the years there have been many myths and misunderstanding about oil, and I'm sure there are still many extant.

I used to believe that it was bad to mix brands or weights. In one of the zillions of oil related threads on this sight some many months ago, there was someone who had vast experience in a lab involving oils and additives who indicated that one of the SAE specifications that oil must meet is mixability(sp?). Although I still don't do this, and avoid it in everything I own, save for maybe the rototiller, I don't think it is harmful.

Good luck,