DIY / Maintenance

Don’t check your oil when cold

While driving in the middle of NC between DC and FL, I made the mistake of checking my oil. It read low, really low.  I panicked and added some oil.  Later I was racking my brain over why the oil level seemed to vary so much depending on the reading.

If it was cold, over night cold, the dipstick indicated too high.

Right after running oil seemed too low.

20 minutes after running the oil was in the middle.

And so I wanted to test it out.  I filled the oil to cold full.  Within 30 minutes of driving I got a "check oil at next refueling" message which roughly translate as I understand it to add 1 liter of oil.

I went further down this rabbit hole and found Mercedes recommends in the owners manual running the engine until hot, then waiting at least 5 minutes to measure the oil.  This seemed to indicate a bit high to me.  When filled to this level the engine would rattle a bit more and was noticeably louder.

I would guess the best way to do it is to drain everything and set to specifications 8 liters.  I will add some pictures of what I would guess the correct indicator is when cold, hot, and just right.

Leave a Reply