Amsoil AFL or EFM for 2002 MB ML320

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Sep 7, 2010
British Columbia, Canada
I have a 2002 ML320. I've put 30k kms on it. (Currently 98k kms on the odometer.) For the first oil change after I purchased it, I put in Amsoil AFL, which they are now calling mid-saps. (I realize the vehicle does not call for oil meeting MB 229.51, but I had some of this oil for another vehicle, so I used it.) I used an OEM synthetic oil filter. Also, not long after I purchased the vehicle, the rear main seal started leaking and eventually got bad enough to require replacement. I ran the AFL oil for two oil change intervals. For the most recent oil change that was done after the rear main seal was changed, I put in Amsoil EFM which they are calling full-saps. Initially, with the leaking rear main seal, I couldn't tell if the vehicle was using oil (as opposed to leaking it), but lately, with the real main seal fixed, it appears to be using oil, approximately 1 l per 1000 km, which in my opinion is excessive. Is it possible using AFL instead of EFM could have contributed to oil consumption?
Did you you change spark plugs? Are the recessed? If so, did you ensure ALL debris was removed PRIOR to removing plugs? IF not, you may have allowed dirt,sand, etc,. to fall into the combustion chamber, consequently scoring the cylinder walls.
I did change the spark plugs (all 12), but I used a compressor to blow around them first. The engine is quite clean, so I don't think any debris got into the cylinders. I have heard that these engines can require valve seals.
I talked to a mechanic who works on MBs and other German cars. He contacted an MB service technician who said there is well-known problem with these engines where scoring occurs on the thrust side of the even numbered cylinders, usually cylinder 2 or 4. They recommend looking in the cylinders with a borescope to see if there is scoring. I don't have a borescope, but I did save some oil to send to blackstone for analysis.
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