if thicker oil is used you will have worst the proublem i have had the same proublem when it is cold it gets thicker that is just common sence you are useing the rite weight oil 4 the winter months like you said with thiner oil the lifters get pumped up quicker cause the oil can flow faster and you it is true it will not hurt the car but over due time it will do damage what brand oil do you use and a car and lucas is a (*bad idea*) cause in the winter months the oil is thich and that stuff is the thickest stuff i have ever seen and in the winter months because on cold start ups you willl have no oil flow at all... and that will lead 2 the lifters not geting oil like they should i run 10/30w mobil 1 what is recamended in the brand new vetts and gto from g.m wit a mobil one filter and my proublem went away....