Dear All: What is the best type of oil to run in my 1990 420 SEL and how much should be used and is changing every 3000 miles/ 3 months necessary if I only put 150 mile a month on the car? Thanks for all your help out there!

Oh boy. Before the various opinions start pouring in you might want to do a search.
Try the keywords "Synthetic" + "Oil" + "Best" + "Change"
then sit back and enjoy.

just go with 15w40...

Opinion # 1.
Have a look here:
http://www.whnet.com/4x4/oil.html

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2007 C 230 Sport.

Dude.....Read your owner's manual, and any quality oil meeting the specs listed will be suitible. There are a million opinions about oil and change frequency. Supposedly you can extend the change frequency with the synthetics but for peace of mind, I always stuck to the scheduled changes. After reading the posts, you will be more confused than ever. My head is still spinning after I posed that very same question for my Harley. End result was I stuck to the oil I had been using for years...NOT Harley. Amsoil has some interesting reading regarding oil and MBs

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I really gets fun when they all don't run

84 500SL
99 Jeep XJ
93 Jeep YJ
03 Custom Softail

Dear Guys- Thanks for all your help, I just purchased my Benz used without a manual but the "search" revealed a plethora of info. Alas, I am swimming in info. Have a good evening- "Dudette" signing off!

Since you only run 150 miles a on the car you have to change the oil by time. Once a year or every 6 months depending on what you prefer.

I don't drive my SDL that much anymore and change the oil every 6 months regardless of mileage. Lots of collectors do this as well.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200