Just got my '88 560 SEC back from the shop for an oil change and some other things. The shop asked, and I specified synthetic oil. When I asked what kind of oil they put in the car, the shop told me Castrol Euro Blend 5W-30. The owners manual specifies 5W-30wt only when it's 14 degrees F or below-unlike the SF bay area where the car lives. The car doesn't leak and has 171,000mi. Oil pressure seems normal-the gage is usually pegged but at idle when warm drops to just below 2bar. When I balked at the viscosity, the shop manager told me they put it in everything and MB recommends it even for my car. Do I risk permanent harm by leaving this oil in the car, or should I change it pronto?

Not a professional opinion but if this is the first time it's seeing -30 oil I'd change it to 10W-40 or 20W-50 today. If it's had -30 for a while now I'd be less concerned.

Oil pressure above 1 bar at idle is fine. Rule-of-thumb minimum is 1 bar per 1000 rpm. You'd probably be concerned enough to have it checked before it got to that point.

Sixto
93 300SD

I'm not taking any chances, today I changed the engine oil to Mobil 1 15W-50 synthetic. Man these engines hold a lot of oil (I'm used to a Ducati). Pull the plug and it's still draining 5 min later-almost completely my drain pan.