Hi guys, my bmw e60 n52 petrol engine got sludge problem... recently i guess due to this sludge caused rpm unstabil and etc... I know about this Sludge problem since two years ago, and tried a few rounds short OCI , around 5k to 7k km already change oil.

Always been using Enoc Protec 5w40 full syn from my usual workshop. Two years down the road, still the same sludge, compared to previous photos from two years back, i think the sludge issue does not improve although i shortened the OCI...

Now im thinking to go a few routes to improve my engine condition:

Option 1: liqui Moly engine flush, but heard that its risky?

Option 2: Use High detergent Engine Oil, (like Shell Rimula R6?), and do a few extreme short OCI , 2000 km change once, for like 3 or 4 times... ?

Option 3: Switch to Shell Helix Ultra 5w40 from Lotus's (cheapest full syn from reputable brand and shop), and do short OCI like 2000km, for like 3 or 4 times... ?

Really worries me as I dont want to leave it just like that, and end up have to overhaul engine...