I am changing the oil in my 1987 420SL every 3000miles which is proving costly.
I need to know how much oil is needed for the change. My dealer charges nearly £35 for the oil alone and I'm hoping I can save a bit by buying it elsewhere.


------------------
1996 SL280
1987 420SL

Most likely near the end of your owner's manual, you should find listed the engine oil capacity figure. This information is also available in M-B and third party shop manuals.

If you are going to change your own oil, I would most certainly recommend changing the filter every time.

In my experience (in the USA), dealers generally charge a hefty premium for the oil they use and in my opinion, though they usually use "acceptable" oil, I typically use a better brand and sometimes a different grade.

Good luck-

The engine holds about 8liters of oil, oil change intervals should depend on driving habits. Most cars can safely go 4-6k miles between svc.