I've been reading a ton of the old posts on the Edmunds board about extended intervals, and thought it would be a good topic on here, especially with the new SL rated oils out now. What oil change intervals do you guys feel are safe with these new SL rated dino oils? Are 5k intervals well within reach for most people now, since the SL rated dino oils contain the new Group II+ base oil? (they do all contain this now right?) So if a dino oil can go this long, what about an oil like Maxlife? It should be able to handle 6k then correct? And regarding the true synthetics with group IV and group V, what would their upper limit be? 15k? 20k? (I know Amsoil says 25-35k but I find that a bit extreme) And one last question, what about the oils that claim to be synthetic but use a Group 3 base oil instead? What kind of interval could they handle? I realize that each particular application would be different, depending on the vehicle used, climate and condition of the engine itself, so I'm basically looking for general ideas, and also thought this might spark some interesting conversation. I asked my father in law yesterday how often he changed his oil and he said 3mo or 3k, almost without fail. People are just so trained to think that way, even though oils are getting better and can definitely go the distance.