Finally took the plunge: 4 gallons of Amsoil AME 15W-40 for $65 (!) to use in the 1991 420SEL. I have been using 8 quarts of either Pennzoil LL or Delo 400 for the last 3+ years with 5K filter+OCI's, and two Auto-RX treatments have already been completed. It uses a miniscule amount of oil in-between changes, perhaps equally divided between an occasional droplet seen near a valve cover gasket or the oil pan and what I consider to be "normal consumption" for a 145K MB V8. Oil always "looks good" at drain intervals. A couple questions, please? What is your expert recommendations for a new OCI and/or filter changes? I'm not really interested in getting into the oil analysis regime (no offense, Terry, et al) but more interested in just a reasonable extension of the fine service I have been getting from HDEO's. Mercedes does (did) indicate both a gas (SF, etc.) and a diesel (CF, etc.) spec for these engines, way back when. Factory OCI was 7,500 miles. Oregon is a pretty mild climate... So what do you guys think? Can I go a full year OCI, which is now about 10K? Stretch it to 15K with a filter change at 7,500? Oh, yeah... I had done a search on this Forum using "Amsoil" as the factor and there was a comment by Too Slick vis-a-vis the AMO 10W-40 product being A-OK for wet clutch motorcycles which appeared (to me) to possibly have been mis-interpreted to mean that the AME product was superior: AME doesn't carry the JASO MA rating and the AMO does. Which is your recommendation for that specific application? Thanks in advance for your clarification.