I just bought this 2005 lly and I was checking over the fluids and I decided to smell the oil, it smells like onions or maybe gear lube. Has anyone else experienced this?
Someone mentioned it could have a quart of gear lube dumped in to make a knock possible go away.
I changed the oil with mobil delvac 1300 super 15w-40 yesterday. I drove it 15 miles to work this morning, checked the oil and it still had the smell of what I smelled before. Drove great and sounded just as quite.
I have been doing a lot of searching around on this topic and found a few possible answers. Somewhere on a Cummins forum someone noted that shell rotella had an odd sweet onion / gear lube smell.
I have also read that zinc-phosphorous can smell like what was described, which I believe shell rotella has in it. ZDPP is also an oil additive that is basically zinc-phosphorous. Sulfer can also smell like this another user online stated.
I'm hoping I am just paranoid at this point, I will have to see what happens with the new oil in it, the smell might stay for a few oil changes also who knows?
When I got the truck the oil was probably in there for 5,000 miles or so (just based on the % ) and I drove it for another 1500 miles, so I'm thinking someone just didn't change the oil and dump some oil honey in it to make things less noisy, but who knows. It has never smoked odd, sounded odd or anything. I also got about 19 mpg on a 3 hr trip and have been averaging 17 mpg the entire time. I'll update this after some time.
One question, how long does it take for your guys oil to turn black after an oil change?
Thank you!!
Duramax Oil smells sweet / onion / gear lube
- Thread starter Duramax44
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Gear oils contain sulfur and smell to high heaven. Motor oil typically does not, in my experience.
The oil in the diesel can be black the next time you check it.
dnewton3
Staff member
Unless the problem is gross in magnitude, aromatic "sniff" tests are a poor way to tell what's right or wrong with the oil. If you suspect a problem, get a UOA.
Welcome to the board, BTW, from a fellow Dmax owner (2006 LBZ).
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As mentioned by dparm, gear lubes are high in sulfur. Accompanied with high pressures and great varying temperatures as well as other contaminants, that sulfur will produce sulfuric acid in your crankcase. Gear lube in a crankcase will cause corrosion even in the most mild internal combustion engines. As dnewton3 points out, get a UOA. With gear lube present in your crankcase with as little as 2000 miles you will notice a TAN quite possible above your TBN. And as many know, that is sooooo bad for your engine. LLY's and LNM's produce what could be interpreted as a knock, when it really is an exhaust sound from the hot side of the EGR. This knock can be heard in the passenger compartment but not when staring under the hood.
As stated before, get a UOA for peace of mind.
Thank you all for the replays but I'm new to the forum and new to all of this oil talk so just a little help here. I understand the uoa is an oil analysis.
What is a TAN and a TBN?
Thanks again
dnewton3
Staff member
There is a a lot of info in the leader pages to this site; please take some time to enjoy the volumes of reading!
Here is just one: http://www.bobistheoilguy.com/engine-oil-analysis/
Many excellent contributions from members and sponsors from over the years.
TAN is total acid number; TBN total base number. Relative indicators of acids and bases in the lube.
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