Bill 12/29/2012My professional opinion is the noise you are hearing is the tappets until the hydraulic lifters pump up enough to quiet them, thus oil type and viscosity is important especially during the cold season. Try a lubricant like Castrol Edge 10-40W and use a WIX oil filter. See if this makes any difference. If you live in Alaska go down to a 5-15W. As you know as the engine gets worn all the crankshaft bearings, camshaft bearings,etc, get worn and clearances grow ,thus reducing oil pump pressure since pump has to work harder to keep up pressure. I am also enthusiastic about a product called Greased lightning as an additive. Hope some of this is helpful.