Any one or any combination of the following could indicate an engine with sludge build up:

-blue smoke from the tailpipe upon start up
-blue smoke from the tail pipe upon acceleration
-blue smoke from the tail pipe all the time
-rattling noise from engine
-knocking noise from engine
-oil leakage from engine seals
-oil deposits accumulating on the intake manifold
-oil seapage from induction plumbing
-gummy, blocked, or broken PCV hoses
-oil consumption
-oil warning light illuminates or flickers

It is also possible to suffer catastophic engine failure without noting any of the above symptons. For a comprehenisve overview of the sludge problem, please click here.

If an engine is verified to be free of sludge, a proper oil maintenance program must be observed by changing the oil every 3000 miles using only synthetic oil and MANN brand filters. For more information on how to determine if an engine is free of sludge, please click here.