I just recentlly change from Rotella 15w-40 to Mobil Delvac on my '96 after using the Rotella for the first 105k. The Rotella rarely got darker than a dark brown. After 3K on the Mobil it is coal black. This bothers me because I'm not sure why even though every other diesel I've seen is this way. I own a Goodyear store so I get to see ALL SORTS of applications. I service all the diesels with Rotella and switched to Mobil thinking it was better based on what I have seen with the gas engines and because a trucker told me the Mobil quieted down his when he switched. In fact he told me he breaks in his trucks with Rotella and then switches to the Delvac Mobil. My oil Rep. isn't even sure but he did offer to do an oil analysis and get me the results. I'm thinking about going back to the Rotella, but wanted to see if anyone had any feedback. I'm thinking one of two scenarios:
1. The Rotella wasn't doing its job and the inside of the engine is full of soot.
2. OR the Mobil isn't doing its job and possible allowing the engine to produce more soot.

When I fixed the Killer Dowl Pin problem while installing the bigger fuel pump (about 10k ago) everything was CLEAN inside the front cover so I'm miffed.

 

The color of oil has very little to do with its lubricating properties. Just because the Delvac turned darker eariler doesnt mean that its not doing its job.


I dont like Rotella myself because of the stink.

 

Stink??? Lost me.

 

When the engine oil in a diesel turns black it means its doing its job and collecting soot.

 

Well that's what I though, too. Doesn't explain everything out front being so clean. Even Rotella bottle say "Advance Soot Control" but does that mean the engine is producing less soot with Rotella or that Rotella is supposed to be molly maid of the internal compustion engine?? If the engine produces less soot with the Rotella than with Mobil which is better??????

 

Oil does not affect how much soot your motor makes only how it disperses it and detergent/dispersant additives are naturally resistant to soot. It keeps soot particles suspended independently, preventing them from attaching together to form larger, wear-causing particles. Viscosity increase is minimized and soot related wear is controlled.

 

Makes sense...I hope that doesn't mean the inside of the engine is full of junk. I think I'll take my rep up on his offer and find out what all is in the oil just for the sake of knowing. I'll get back with the results. In fact I'll do it with the Rotella as well. May take a few months but I'll do my best to let everyone know at least what my Cummins is doing.

 

I don't think you have anything to worry about. Probably the detergent additive package getting some of the stuff the Rotella left. Not particularly good or bad, just one of those things.

Oil analysis is a good thing if you do it on a regular schedule, track trends. On a one time shot, it'll tell you if there is anything real weird going on but you get your best bang for the buck by doing it regularly. Can be a good tool or can be a waste of money, all up to you.

Changing oil brands isn't a real big deal anymore. Our company recently switched from Fina to Exxon, couldn't tell the difference in most engines, one of our folks who drives a '00 GM 6.5 noted that at oil changes, the Exxon seems to be a little cleaner than the Fina coming out the drain plug.

 

Synthetic has many detergents in it, this is why it is darker. I like the smell of it.
Brandon

 

I forgot to mention - there is some real good reading on oil here:

www.bobistheoilguy.com

 

Did you change oil filter brands too? Maybe the Delvac binds tighter to soot particles than Rotella so less soot gets trapped in the filter.

OR maybe it gets darker because it started out darker.

 

I dont know much about what is in oil but between me and my dad we have been working on big diesels for about 50 years. So we have been able to see insides of engines that have run every kind of oil. Diesels that have run Rotella look the best on bearing wear. Thats my 2cents

 

Could be the Rotella was rated CI-4 and the Mobil CJ-4.
The new CJ oil is designed to hold more soot.

 

Not to start an oil war, but I will take issue with your comment "switched to Mobil, based on what I have seen with gas engines". That was most likely the Mobil of the past. After losing two cams on the dyno, on consequtive engines, I got suspicious. A bit of research on this great forum brought up a terrific article from L&N Engineering.com that explains it. The powers that be are dictating that for the sake of cat. convertors, the oil companies reduce the PPM of Zn and P. These are the two elements that have been protecting our cams and lifters. The good news is that the diesel oils are being left alone, at least for now. Worth keeping an eye on.
Just had a conversation with a svc. manager yesterday who stated D&C are rescinding their statement that the 600 CTDs can go 15K between oil changes on schedule A useage. Any comments on this?