Well...I'm in a rather awkward age to answer this question! At 18, there could be some legal complications with dating someone younger because they're not of age. But age matters more in the teen years, and the youngest guy I've been interested in was 1 1/2 years younger than me.
As for older, my dad candidly told me he would flip out if a 26-year-old man asked to date me
. Personally, I don't think I have a problem with an 8-year age gap, especially as I matured fast and men (in general) mature more slowly than women.
Speaking from the vantage point of my hypothetical 35-year-old self, I'd say I wouldn't have a problem with 6 or 8 years either way.