I change just the filter really early...first couple of hundred miles. I always find lots of particles caught in the filter (yes, I've been cutting open filters since the 1970's!). Then, I go a couple of thousand miles and switch to a synthetic. NEVER have I seen a dirtier filter than the OEM one...which makes perfect sense. On some motorcycles, there is a pre-filter screen that can be removed and cleaned. Talk about trash caught from the initial break-in! It's sometimes simply horrendous. No matter what engine, I've found that particles caught by the filter decrease the first couple of changes before settling out to very little the rest of the time I've ever owned it.