Have a hi mileage 196K 83 500 sec & was thinking about synthetic oil.
Also I have been reading that older engines need zinc in the oil which is not included in current oils except some diesel spec oils.

Whats best to keep a older 126 engine running its best?

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83 500 SEC Euro 198K

Synth is great, but reading all the other oil thread would have told you that too.

Zinc is used as a lubricant and to help keep your oil basic (pH). There are plenty of other lubricants (better), and other pH buffers, zinc is old-school but works fine.

Lots of good syn oil out there. The plusses are: lower friction for better fuel mileage and less engine wear; faster pump-up when starting cold for less engine wear; lower viscosity at super-cold temperatures (not your problem in CA) for easier cranking; cleans engine out for better lifter operation and less gunk build-up; and extended-drain intervals for less environmental impact if your engine is running properly.

Minus is mostly cost. The "it will leak if you change a high-mileage engine to syn-oil" myth is from the '70s when it did different things with seal swell than dino oils and wasn't compatible with dino oils, and the fact that it will clean gunk and exploit existing leaks better. Mercedes' official stance some years ago (technical seminar published in The Star) was if it leaks on syn-oil, change it back or try a part-syn like Castrol Syntec et al. It will go back to its old self.

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Gone to the dark side

- Jeff

All benefits, no problems. The biggest benefit for me is the 7-10k mile oil change interval.

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CENSORED due to not family friendly words

Thanks
Guess I should go for it then.

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83 500 SEC Euro 198K

Well, my engine (M103), has so far responded extremely well to Mobil 1 0-40W. Within 2 days of using it with a Knetch oil filter, all of my top end valve noise that was usually present upon cold start up disappeared. The engine does seem much more smooth, but that could just be me wanting that and thinking it is there... The valve noise was real, and is really gone now!

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)

To begin with the zinc issue is for older engines with FLAT TAPPET cams. Your engine does not have roller followers, or a flat tappet cam. It has a sliding mechanism which offers more area for valve spring pressure to be distributed. The zinc additive would not be a bad idea, but since it's broken in, it is probably not a problem.

If the engine is not using oil, then you could probably get by with extended oil change intervals with syn. If the engine DOES use oil, don't plan on extended oil change intervals. The blow by will contaminate the oil requiring shorter intervals.

Personally, I believe you would be better off using a premium dino oil and changing it more often.

My $0.02,

While flat tappets.. versus rocker arm stuff- it's still sliding contact instead of roller...

I don't like any oil which says energy conservation on the label- I don't want it to wear out early. I would use synthetic diesel oil(Mobil 5W40) or Delo400.



Michael

I have some tapping noise
would love to help the engine as best I can & if a more lubricating oil is the trick then I'll bite.
I don't know if it uses oil as I have really not driven it much
It doesn't burn oil or smoke & oil pressure is good.

Plan to finally take the beast on the highway
I've been afraid
yeah call me a worrychondriac
but the car was meant to take to the roads not to look at like the work of art it is

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83 500 SEC Euro 198K