PeachParts Mercedes-Benz Forum - My CDI Oil Analysis

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Oil standards have changed as engines have changed, as mentioned above. Modern engines run different combustion temps, have catalyst systems not present on older cars, and burn much cleaner which contaminates the oil with less fuel and soot.

Additionally, manufacturers are building engines to tighter tolerances, and specifying thinner oils for less pumping losses and shear/frictional losses to improve fuel efficiency.

Finally, fuel has changed. The changes to LSD and ULSD have meant that there is less acid produced, and the old high-TBN oils are actually bad for the engines and unnecessary.

Hard for many of us to keep up with the changes in oil specifications, but in most cases using a diesel oil in an older car with a newer oil spec/approval is adequate or better for running ULSD (which includes off-road fuel, also ULSD these days) provided it is CD rated and the proper viscosity.

Exchange TDT for 0w40

I took some of the TDT I stocked up on during that great sale into Walmart recently and just exchanged it for 0w40. I told them it did not meet Mercedes requirement for my car. They said "no problem".....now I have oil that meets MB requirements for 648 engine and I got a 25% bump in volume to boot ;)

Quote:

Originally Posted by DieselPaul (Post 3617972)

That's a killer deal on M1 TDT!

3k drain intervals on a motor as modern as the 648 is an incredible waste of oil but its good for you the next owner of the car.

It is actually my understanding that the 229.5 spec is more for the emissions system of the modern engines. The 229.51 spec for the bluetecs (or like VWs 507.00) is all about protecting the DPF. Using a non 229.5 oil you're not, not protecting the engine, but you may be damaging the Catalyst or clogging up your EGR cooler faster. But that's just my speculation, I suppose I'm basing that on no real data. In my world I don't have 40 gallons of M1 TDT on the shelf, nd the 0/40 Mobil1 229.5 oil is the same price as all the other oils (might actually be cheaper since it comes in 5.1qt jugs) I have just always run that in my CDI.

I'm in no way saying M1 TDT is a bad oil, and I understand the anti-wear additive aspect of a 228.x spec oil, but with modern emissions controls and filters, that is not the whole picture. A 228.x oil would be a killer oil in say a W123, but it could also very easily roach the DPF in a Bluetec car, which the DPF alone is worth more than most of our 123s. So it worth thinking about. 648s don't have DPFs, so this all may very well be a moot point.

Regularly changed Mobil Delvac conventional oil would probably "protect" the engine itself just the same if it was changed at the right intervals.

Just food for thought, I appreciate you posting your oil results, good to hear the 10,000 mile intervals on a quality oil in the OM648 are well within the realm of reason.

That UOA looks great. Im almost not believing how low Pb, Cu and Al are... Fe looks fine... Soot at 0.13% means there is so much retained dispersancy, that since the oil didnt go out of grade, you can go much longer. Id not condemn until out of grade, too low of TBN, or soot >1%. Wish we knew TBN...

Comments on TBN from OA tech: "TBN measures the reserve alkalinity left over in an oil after it has been in service. Used to be a real big deal with high sulfur fuels as they tended to leave the crankcase oil very acidic. TBN is still a factor but more so due to to nitric acid build up from the combustion process. It can sometimes be a factor in heavy duty trucks using EGR or SCR technology after high heat conditions. We still measure TBN, but rely more on TAN as it measures the actual acid content and TBN only measures remaining reserve in oil. Typically your oil is a 10.1 TBN and normally drops down to a 8 or 9 if the condition is extremely severe. I typically do not request that level of testing unless the drains are really extended such as 50,000 mile and above with commercial vehicles."

Not sure I agree with that.

Yes, that oil should have good TBN retention, lots of buffering capacity...

And yes, with lower sulfur fuels, the acid formation/tbn loss is slower.

In low SAPS oils in gas engines (gasoline has higher sulfur content currently), we have seen TBN go to a condemnation level in ca. 5000 miles.

Diesel has roughly half the sulfur of gasoline, and HDEOs have higher starting TBN, but Im not seeing a 50k mile equation here even if an MB sump is 2 gallons. For whatever reason, sometimes you have to write it in multiple places to remind them to do it, other wise they wont give you the testing you actually paid for...