Mine does it too, it's a 300 with 45k miles. I've been a mech. my whole life & know it's bottom end,(mains/rods). It's mostly drain back after 8 hr. of sitting, worse in winter, worse with Mobil 1 than reg. oil. I use oem filters supposibly with a built in check valve, I sure don't like to hear it but don't think replacing bearings is nescessary or would even correct it.