So had a screeching/high pitch buzzing noise start coming from my oil filter housing and sure enough the filter (recent Mahle) was plugged with fine brown crap like you would find on the inside of the valve cover. A week or 2 earlier I went to get some 15w40 oil to add to try and diagnose more what's going on with my sometimes noisy lifters. The only brand name 15w40 they had in stock was Rotella T and I even talked to the parts guy about how Rotella T back in the day was known to have high detergent and was good for cleaning out engines and how Castrol was known for creating sludge so should be perfect since previous owner likely used Castrol! I only put about a 1 1/2 liters of "T" in and even though I knew what might happen I wasn't ready for it to be so quick! The filter sure is tiny though and maybe being a Mahle was on the fine side. Just before the noise started I gunned the engine a bit on the highway and something didn't seem right as if the timing got cut back and sure enough now have some knock codes! It's all good now though, power is back and lifters are totally quiet!
Hopefully it stays that way and I didn't shorten the life of the engine too much!