A few weeks ago I changed my oil on my 99 Chevy Astro with 98000 miles. I start engine and everything is fine. Than a couple nights later I go to leave from my inlaws and the outside temp is 35 deg. and I hear this knocking on startup. My oil pressure is good and the knock goes away after 10-20 sec. The next couple days same thing happens. I'am thinking its the wrist pins or something else. Well I decided to start easy and change the filter again thinking it could probley be the oil filter. Well guess what? It is. Old filter was a ac delco 52 and new one is a wix. Problem solved.