Mobil 1 does NOT guarantee anything (read the disclaimer on the bottle). Mobil 1 EP has more cleaning and other additivies but there is NO WAY I would use it for one year or 15k in my car.

I change my fully synthetic oils (10-40 in summer and 0-40 in winter) every 4k with Mobil 1 filters. I use Castrol Syntec 10-40 in summer and Mobil 1 0W-40 in the winter.