Topping up is a normal practice. I don't see any problem with adding, but if it burned off that much, maybe you need a thicker oil in the future. Is what remains in the crankcase pretty nasty? If so, I'd want to get it out. Otherwise, top up, but if you are changing it next week, I would use low priced oil, whatever is on sale today, but in spec (SL, not SA).
[ February 27, 2004, 12:30 PM: Message edited by: TallPaul ]