I was on the MBCA board answering a question regarding what oil to use on a FSS car that was a diesel. Now this is not a oil question, so lets not start any flaming. What I would like to know is WHY is syn. oil mandated by MB. Maybe I don't fully understand the FSS system, but it seems to me that the system basicly tells when your oil is due for a change based on the condition of the oil. Why then would it matter what type of oil is in the crankcase. Granted the viscosity of dino oil won't last as long as syn., so the "service oil" sign would come on sooner. Unless their FSS system is seriously flawed and mandating synthetic oil is a way to cover that. I know that MB just got class action suit brought against them over this. To me IF the sys. is working as it should, then those who choose to use synthetic, will go longer before the "service oil" sign comes on, versus a convential oil user. Just something I was wondering about. Any FSS car owners out there who may be able to shed some light on this.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member