Hey guys, new to forum. I have a problem. When I start my Altima it sounds fine when cold and at idle. Rev it up over 1500 -2000rpm and I hear a little valve clatter. Under load I hear a lot more valve clatter until the motor reaches operating temp (or close to it). I have checked the oil and its fine. I have been using 5W-30. The engine has about 36K on it. This noise has always been there during cold starts but its wasn't that noticeable. Now that its been very cold out (I live in St. Louis) the noise is more noticeable. I had brought the car in to Nissan dealer and got the runaround. My Altima is also a 5spd stick if that makes a difference. I wonder if this possibly could be an oil filter problem. I have been using the Super-Tech oil filters from Wal-Mart. I know that's probably not the best idea. Could it be that the bypass valve in these filters isn't working correctly (not opening and bypassing the filter in cold weather)? Would dropping to a 5W-20 oil help or going synthetic help? Or is this a different problem all together? Thanks for your help.