Originally Posted by tinypanzer

I personally use either Mobil-1 10-40, or Castrol Syntec 10-40 in my '90 300SE. I am told (I hope correctly) that the cam metallurgy changed for model year '90 and up and that the zinc additive was not necessary for this motor. I sincerely hope that is true! I was told this by senior members, and so I believe it.

As to filters, FRAM sucks. That's not just my opinion. Go to one of the oil filter comparison websites and see what's inside one. Cardboard garbage.

I recommend OEM, Purolator, NAPA, Dana, Wix, K&N. K&Ns are great filters, but they dump oil when removed. Purolator is a great filter with good components but a slightly thin casing which can be dented by your thumb during installation if you squeeze too tight.

My M103 oil strategy is a bit different because I lose about 1qt every thousand miles. So I don't drain very frequently, I just keep it topped off and replace the filter periodically. Keeps the oil nice and blond.

Advance and AutoZone often do 5qt plus a filter for $X deal. I usually grab this when I can just remember that the M103 is a 7 quart oil glutton. So, I'll buy 10 quarts of synthetic and two filters for about $50. That lasts me for over 6 months, with two filter changes and the oil stays fresh and clean. But that only works because my rear main seal is shot, and I lose oil. Once I get that fixed, I'll have to go back to drain/fill.