I guess I have to take a step back and ask why you're only talking about SPF 8? If you're trying to get a tan or burn and look "summery" SPF8 won't do much to stop it, so you might as well skip it.
If you're trying to prevent skin from aging prematurely and prevent skin cancer, going with an SPF of 50+ (the highest you can find) is probably worth it (especially since there is little to no cost difference between the different SPFs).
I started wearing sunscreen in my teens, every single day even in the winter, and nowdays people think I'm at least 10-15 years younger than my actual age. I've also never had skin cancer or other such problems that plague both sides of my family. Just something to think about.