If the fuel pre-ignites, proper flame propagation will be thwarted, and the fuel will not be burned as thoroughly, leaving residue, and exhausting (albeit tiny amounts of) fuel. Sure, I put the cart in front of the horse, but I can always count on HN to point out the pedantic.
Reading this again, you're right, it was a little pedantic. This is one of those topics I feel is just rife with misinformation, so I tend to jump on explanations that don't seem correct at first glance.
