Yarn yardage with different size needles

[maggie_g]

Hi, I have a pretty basic question I just can't wrap my mind around. If I do a scarf on size 6 needles when the pattern called for size 8, will my scarf be longer or shorter if I just go to the end of the skein as the pattern directs? In other words, do you use more or less yarn per row if you use smaller needles than directed? (I tend to knit loosely, that's why I went down two sizes. But I think my gauge is smaller than the pattern's.)

Thanks so much,
Maryann

[Abbily]

OK, someone check me on this, but... if the needles are smaller, that means each stitch will be smaller, and will therefore use less yarn. Meaning each row will use less yarn, too. Right?