Hello to everyone, since this is my first time writing in this forum. recently i bought a 1995 E320 and a 1987 190D from a guy who worked himself on the cars. I plan on doing the same thing, and this weekend I want to change oil and filters on the E320. From looking in his receipts, he used the same oil type on both the 190D (which is a diesel) and on the E320. The oil he used is Mobil Delvac 15w40, which is for diesel cars as far as I know. The E320 engine has been running on this oil for a few years as the receipts tell me. I live in an area where it snows 3 months a year (South Dakota). Should I continue to use this oil, or change to a 10w30? I don't really want to change the oil brand since it always has used the same oil, but if I have to than I will. Also sometimes when I turn on the E320, i hear this little knocking noise (like the noise a diesel makes, but not as loud), not always, only sometimes, especially in the mornings. Could it be from the oil or oil filter (it has Mann oil filter in it, and that's what I plan on using in the future), or is this normal for its age/mileage? Other than that the car is in top shape. Any comments would be greatly appreciated.

moss,

the 15w40 will be fine down to 5 degrees Fahrenheit. if it gets colder than that, 10w40 will be good down to -4.

mercedes recommends 5w50 for all temps for your E320...which would mean switching to synthetic.

you'll probably get about 8 million different opinions but i'd say you're fine sticking with the 15w40, that is unless you see temps below 5 degrees.

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Thanks Ozawa for your reply. I do actually see temperatures below -5, only a few days though. But the owner before me had the car in the same area. I know that it will still start at temperatures below -5F, but is it possible to damage anything like an oil pump for example? Also i don't really want to switch to synthetic. The engine has only seen dino oil in 12 years, and switching to synthetic doesn't seem the right thing to do.
What about the knocking sound, any comments?

Huh?? Where would one find this recommendation?

Those commercial-grade oils like Delvac and Rotella are the best, diesel or gas.

OTOH, I've always used Walmart Supertech with excellent results.

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2012 E350
2006 Callaway SC560

Factory service literature.

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True. For that model, 0W-40, 5W-40, 5W-50 can be used at all temperatures. As a matter of fact, even 0W-30 and 5W-30 can be used at all temps. This is from the 2006 approved service products brochure.

So what do you guys think, Delvac 15w40 will be ok for the cold days in January-February, or should I change to a 5w40 grade?

15W-40 is a bit too thick in the winter where you are. I would suggest 10W-40 or even 5W-40 for Nov - March. The 5W-40 is going to be synthetic.

This will cause some controversy. On my 1997 E320 (same engine as yours), I uses 1 gallon of 15W-40 (I love these universal oil for both diesel and gasoline engines) and then about 3 quarts of synthetic 10W-30 or 5W-30. The purists will yield but I know my engine is not going to fail because I use this brew.

Thank you Loubapache for your reply. I'm leaning more towards using a 10w40 or 5w40 now. Is there a Delvac 5w40 (dino) or a Rotella 5w40?

There is a Delvac 1 5W-40 but it is synthetic.

There is also a Rotella T 5w40 but it is also synthetic.

You can buy the Rotella T 5w40 at Wal-Mart for about $16 per gallon.

Some people will argue what a synthetic really is but these are what the manufacture call them.

Too bad they are synthetics. I don't really want to use a synthetic oil, so I will have to settle with a Quaker State or Valvoline 10w40.
Thank you again.

Any dino 10W-40 should work with 3 - 5K change intervals or every 6 months, whichever comes first.

Please provide a copy.

Rotella has non-synthetic also.

One comes in a blue container, one a white. I don't remember which is which.

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2012 E350
2006 Callaway SC560