My car Civic calls for 5w30 weight oil. It states in the summer 10w30 can be used >20F. I took my car to Walmart and had them change oil with Mobil 1/SuperTech filter however they incorrectly placed 10W30 into it. I know now it does not matter currently in the summer however the oil will be run into December (7500 miles) where temp drops on average to around 30F with occasional dips to 15F. Should I take back (a hassle) or will it be fine since 10W30 synthetic flows better anyway in the cold I imagine than 5w30 conventional (recommend oil).