My sister has a 2011 Jetta and needs an oil change. I would like to change the oil soon before it gets too cold. Originally I planned on using Mobil 0w40 but there are no current oil specials on Mobil 1 at any auto parts shops. Now there are a few good deals on Castrol though. The 5w40 is this cars factory fill oil but I don't see too much love for it on the site. The car will probably go a good 6-8k on the oil and her driving conditions would be considered severe with lots of short trips. Should I pay the extra $ and do the Mobil 1, or will the Castrol do just fine?