I suggest you take a look in the following thread in or [I]Blank Media[/I] forum:
[B]Did you know: [/B][B]Slow write speeds + modern drives + modern media = no good[/B]
With most modern desktop DVD burners and 16x rated DVD media, the burn speeds that provide the best chance of a good result tend to be 6x, 8x or 12x. You can either experiment to find the best speed with your combination of DVD burner and media, or pick something that will probably work.
I burn most of my DVDs at 8x with a few exceptions where 6x or 12x is better.
If you have older 8x rated DVD media, the optimal burn speed in desktop DVD burners is usually either 8x or 6x.
If you have a laptop DVD burner, the optimal burn speed is usually not the maximum speed of the drive (8x) but one or two speeds lower, i.e. 6x or 4x. If you don’t want to spend time testing, I suggest using 4x burn speed for laptop DVD burners.