Best diesel oil - PeachParts Mercedes-Benz Forum

gdl40 · #1 10-19-2019, 02:38 PM

What is the best oil for my 84 300D? I'm now using 15/40 delo diesel motor oil. The car will be in Boulder, Co, and I'm not sure if this is the best for this location.

Sugar Bear · #2 10-19-2019, 03:02 PM

That is an excellent choice, you may wish to source the same in 10W-30 for the winter as it is hard to find occasionally in the 10W-30. If the temps are extremely cold, a diesel rated synthetic such as DELO 5W-40 would be my choice. In very cold climates, synthetic oils make a BIG!!! difference in cranking speed.

Good luck!!!

Father Of Giants · #3 10-19-2019, 04:40 PM

Don't use 10w-30. Any diesel 40 weight oil will work, even 0w-40.

Sugar Bear · #4 10-19-2019, 05:33 PM

The owner's manual calls for 10W-30 from -4 to +50 F., 40W if temps constantly exceed +86 F. A 10W-30 diesel "C" rated oil is fine in cold temps.

Good luck!!!

dude99 · #5 10-19-2019, 06:15 PM

Another bloody oil thread? Jesus... I know forum search functions suck, but all of them will bring up about a million oil threads, which all say the same thing...

Father Of Giants · #6 10-19-2019, 06:49 PM

https://www.thebestoil.com/product/amsoil-signature-series-max-duty-synthetic-sae-5w-40-diesel-oil-api-ck-4/

Screwdriva · #7 10-20-2019, 06:46 AM

Stay away from synthetic oils. If possible, run the Auto-Rx treatment using Delo or Rotella oil. OM61X engines love that stuff. Then switch to the oil of choice.

I've only heard good things about Liqui Moly MOS2 10W or 15W-40 oil. Marketing will tell you that molybdenum disulfide provides superior anti-wear properties that our old diesels love. I believe in a before and after result I believe in.

Tried running it in my injection pump (W115 240d). Results were good so will be my engine oil after the next change.

oldsinner111 · #8 10-20-2019, 07:42 AM

their is a university study,that states Cummins 15w40 is the best,followed by Rotella 5W40
alot of new mercedes diesel were having timing chains break do to newer thin oils,that did not contain zinc,and other minerals

Father Of Giants · #9 10-20-2019, 08:29 AM

Quote:

Originally Posted by Screwdriva

Stay away from synthetic oils. If possible, run the Auto-Rx treatment using Delo or Rotella oil. OM61X engines love that stuff. Then switch to the oil of choice.

I've only heard good things about Liqui Moly MOS2 10W or 15W-40 oil. Marketing will tell you that molybdenum disulfide provides superior anti-wear properties that our old diesels love. I believe in a before and after result I believe in.

Tried running it in my injection pump (W115 240d). Results were good so will be my engine oil after the next change.

https://www.youtube.com/watch?v=oc5i6Vevox4

Synthetics won't hurt a thing.

Screwdriva · #10 10-20-2019, 02:27 PM

Disagree. They leak through old seals ALOT more than dino oil in my direct experience.

The Liqui Moly oil I recommended is not what is featured in the video above. It's MOS2, which is very compatible with classic motors.

Father Of Giants · #11 10-20-2019, 02:37 PM

Quote:

Originally Posted by Screwdriva

Disagree. They leak through old seals ALOT more than dino oil in my direct experience.

The Liqui Moly oil I recommended is not what is featured in the video above. It's MOS2, which is very compatible with classic motors.

Disagree

https://www.youtube.com/watch?v=Pa4RwsiZUmI

Diseasel300 · #12 10-20-2019, 02:42 PM

Quote:

Originally Posted by Screwdriva

Disagree. They leak through old seals ALOT more than dino oil in my direct experience.

The Liqui Moly oil I recommended is not what is featured in the video above. It's MOS2, which is very compatible with classic motors.

A synthetic oil *WILL NOT* make your engine leak. If it does, the leak was already there. The synthetics typically have different/stronger detergents and will make an existing leak plugged by sludge/dirt/carbon into an existing leak not plugged by sludge/dirt/carbon.

You're welcome to use whatever brand or additives in your car, it's your car. If you want to spend 2-3x for an oil with MOS2 in it, go for it! So far to date, it hasn't shown to help anything at all and with the high mileages these engines run without it, it doesn't seem to be necessary anyway. Just don't go around proclaiming the virtues of any sort of a "mechanic in a bottle", you lose all credibility.

chronometers · #13 10-20-2019, 03:13 PM

This is an easy and inexpensive oil to obtain on a consistent basis and you can pick it up in Walmart nationwide. Definitely run it for the recommended oil change interval as it is sythetic....more if supported by oil analysis. M1 0w 40....5 quarts is ~$22.

Screwdriva · #14 10-20-2019, 04:30 PM

Quote:

Originally Posted by Diseasel300

If you want to spend 2-3x for an oil with MOS2 in it, go for it! So far to date, it hasn't shown to help anything at all and with the high mileages these engines run without it, it doesn't seem to be necessary anyway. Just don't go around proclaiming the virtues of any sort of a "mechanic in a bottle", you lose all credibility.

MOS2 is not 2-3X the cost of synthetic oil here in the EU. I didn't claim it was a mechanic in a bottle. I said it has worked well in my IP and that I will continue using it as a result. I also said that synthetic oil led to my seals weeping/ leaking. Mineral oil didn't and doesn't after I switched back. Again, this is on my 4 classic Mercedes vehicles only.

https://www.youtube.com/watch?v=rh0PtXwZo_Q

engatwork · #15 10-20-2019, 05:33 PM

Been a long time since we had an oil thread. As Larry always says, change it hot and change it often.