I use Mobil 1 in my vehicles mainly because I can get it cheap at Walmart and I do my own oil changes to keep the cost down (and I don't trust most 'shops'). I also like to fill the filters before I install them so there isn't a little 'dry' start and the oil pressure comes up faster. In Minnesota, we have winter temps down to -20* and it can hit 100* or more in the summer so I like to use good products. For filters, I will use Purolator Pure One, Mobil 1, or K&N. By doing it myself, I have about $30-32 into each oil change and will change the oil and filter between 3000 and 4000 miles depending on when I can get it done. (I shoot for 3k and make sure to get it done by 4k. Usually, it is less than 3500 miles)
My 2000 Regal GS has 210k miles on it and still runs great. My 1995 Impala SS has 194k miles on it and still runs great and even gets a severe workout on the road course which is pretty stressful on the engine (130+ mph and a lot of time at high RPM's). Our Silverado has 100k on it and also runs great. We drive a lot and keep our vehicles for a long time, so I will pay a little more for higher quality car care products.
Synthetic is probably overkill, but I don't mind paying a little for peace of mind. My old truck went to 325k (or more after I sold it and lost track of it) and that was with crappy filters and regular name brand oils, but at religious 3k intervals. I think regular intervals with any oil is probably more important than which oil you use.
OCD isn't just for detailing......
Randy