Oil ratio is not dictated by the oil, it's dictated by the oil "contact time" So a high revving 80cc needs more lube than a slow turning 500cc..
Typically 40:1 is fine for a 250cc, but varying from 32:1 - 50:1 won't hurt anything.. more oil generally won't create a problem ever.
www.maximausa.com for more info on the correct way to choose a ratio.
Jon!
ps. If I'm going to a track on my YZ250 I'll run 32:1, but if I'm going to be lugging it through some woods I mix it to 40:1.