It depends on the climate between now & the next oil change. 5W is what modern vehicles are built with because it reduces internal friction & raises CAFE. But it's not necessarily the best for your particular vehicle in your particular region/season. And as the engine ages (wears), you should go up 1 level for every 1.5-2Kmi. I run 20W50 in mine right now because it's close to 400Kmi, but I've taken good care of it.
