The brand of oil that you are using could be the problem.. Quaker State is a Pennsylvania crude which is parafin based. I have taken engines apart that have been maintained with QS and they had a silver sludge build up. Change to some other oil and don't go to a higher weight, you will not gain anything. Cold start with thicker oil can result in noiser lifters as the cold thicker oil has a harder time squeezing thru the clearances.
