I've got a 2002 Mazda Protege LX, with a few bolt ons under the hood. Nothing special, just a header, intake, TB spacer, ported TB, plug wires, and soon an AFC. The car sees city driving 99% of the time, and it's all short trips. Once a month or so, I'll take it on a Sat morning freeway run, for about 20mins. My "commute" to work is a whopping 5 miles each way. On the weekends I drive a bit further, and for longer periods of time than the 15mins it takes to get to work(dang traffic), but it's all city driving still, and still considered short trips. Oh, and I drive very hard. Lots of hard acceleration and the like. I do let my oil come up to temp before the thrashing begins though(I've got an oil temp gauge). The car does see freeway speeds(or close) depsite my driving in the city, usually around 60-ish, but not for very long. I've been using Castrol 10w30, and my OCI's have been every 3months. No analysis has been done(gotta do that). My question is : Am I changing my oil way too often? What OCI would everyone reccommend for regular oil? Would I be better off paying for synthetic, given my driving habits?