95 plymouth neon, SOHC. 67,400 miles. i go through moderate stop and go traffic, HOT eather, and in winter, terribly cold. car rusn on 5 w 30 oil use 10w 30 for summer. i change my oil every 3 months, would using conventional oil even under these circumstances, be okay? or would synthetic be the way to go? i am kinda getting edgy about synthetic now, because of my short change intervals.