I recently bought a 1985 300SD and since I have no idea when the previous owner did a tune up I was wondering how often they should be tuned up? Do you need to replace the spark plugs at a certain intervals and when do you do other services?

No offense but before touching that car go over to the diesel forum and do a lot of reading.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

What he means is ... diesels don't have spark plugs!

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

You can buy any brand of spark plug you want. Leave them in the box they came in, put them in the trunk and you will never have to change them ever.

Seriously, the above suggestion is a good one. Diesels don't have spark plugs. They use glow plugs. Get yourself a basic manual and and owner's manual and read about the car. The maintenance manual that comes with the owner's manual packet also is a great way to learn when and what routine maintenance tasks need to be done.

Len
'83 240D 345,000 miles original owner

They are 100% correct. For diesel engine questions, it is best to head over to the "diesel" forums, but this forum is excellent for anything else concerning your car, from the body, brakes, interior, etc.

Enjoy your car!