auto travel from Granada to Barcelona in January

You've asked two questions and don't know it. The stated question: The freeway runs along the coast so that chunk won't be an issue. Once you swing inland to the west, you'll probably see snow on the mountains to the south of Granada, but you'll be so low that it won't be a problem. What you missed: Unless my mind has failed completely, that's almost six hundred miles. There won't be much traffic, but you'll need an extra gas tank on the roof that gravity-feeds into the main tank and you'd best skip morning coffee. What I'm unsure of is the status of all the road construction in southern Spain. I was poking around in the area a bit west of where you'll be driving a couple of weeks ago and the roads there were still in the same state of unconsruction as they were a year and a half ago when I also drove the freeway you'll be on. I think what I'd do is leave Barcelona in the afternoon and go as far as Valencia (not a bad place for a stop), then make the rest of the trip the next morning. Granada is not a great place for a dark arrival if you're unfamiliar with it.

I agree with Ed. We did the reverse drive from Barcelona (actually 1 hr south of) to Granada in April. We were quite happy that we stopped overnight in Valencia. We went into town for a nice dinner and a stroll. I feel that 8.5 hrs is a very low estimate for the time needed, a lot like the Michelin estimates and by the way....I drive above the posted speed limit.