Any T680 Owners? Would love some feedback.

Kenworth just switched right in the next month to 10w30 after I got my truck. The w40 is a little bit thicker and provide a more robust protection what I thought help for the fresh engine. Also it was cheap for the frequent changes. The mineral oil degrading faster and the blend means very small percentage of synthetic oil. I do not say they are bad oil, but the full synthetic is superior in any day, especially with these long intervals what is recommended for the new engines. Also the 5w is a little help with cold start and provide a tiny bit better fuel economy. My choice was either more frequent changes or full synthetic. But after the first change to synthetic produced imidiate change in the motor sound. It was so much smoother, I decided I do not put anything else into my truk.

 

You might want to frequent this website and read what a lot of oil and lubrications specialists have to say regarding the synthetic is always best argument.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=cfrm

I don't use Delo, but they have shown extensively their conventional oils going well past 70,000 miles in modern diesels. The 5w30 indeed will be a little beneficial in extreme cold, but fuel economy is not proven over a 10w30. It doesn't matter.... both oils at operating temperatures are the same 30w oil. Both have a viscosity rating of roughly 12.5 cSt at 100C. Only the cold flow is different, and not that much. There is no difference once warmed up. When both have the same viscosity at the operating temp, then how can a 5w30 be more fuel efficient than a 10w30? Not possible to document any benefit out here in the real world. Now your argument works comparing a 30w to a 40w.

I have no problem with synthetics in the least. But likewise, I do not fall for marketing hype either. There have been extensive write-ups done by people that know more than you and all of us here do about oils, that have shown that, except in special applications, full synthetics are rarely needed or provide a substantive benefit to the average user. Several years ago, the differences were tangible. Today, with advances in base oil refining, the gap has closed significantly. So much so that blends today offer more than adequate protection, even at longer intervals, for the majority of folks. And offer the best value.

And the additive packages that are part of any motor oil, are strikingly similar in composition. All major oil brand use the identical additive package for their blends as they do their full synthetics. There is no difference. And since the additive package makes up to 20% of any motor oil, it is a major factor.

 

Most of your claims are true, the synthetic blend with the factory recommendation is likely adequate. However I feel uneasy about the recent dramatic increase of the oil change intervals as most mechanic does. Thinner oil, dirtier air, (EGR) , almost three times longer interval make me skeptical. I do not see in our engines what justify this dramatic change. Since I want to keep my truck for a looong time, I wanted more than adequate plan. This was more frequent changes or full synthetic. I chose the latter. Now, I happily discard oil, what is still perfectly fine to run, and I do not spend more on oil change than I did on my old Detroit. (15,000ml, 15w40 conventional.) The good lubrication is just too important, especially with this highly complex engine and after treatment system.

 

But all you mention centers around the additive package of the motor oil. Soot control, anti friction components, acid control, emission control protection, etc and holding up under longer intervals is the arena of the additive package. The base oil itself rarely ever breaks down except in the most bizarre of circumstances. The add pack components are what wear out of break down. I will agree that blends and full syns generally have stronger add packs than the conventional oils, but that is about it. I have checked with several oil companies and they confirm that the add packs they mix in their syn blends are identical to the add pack they put in their full synthetics.

And that is where the marketing folks confuse the user. They convince the owner that the base oil is what one has to worry about, and rarely ever spend time on the additive package that is part of the motor oil, like molybdenum, calcium, sodium, antimony, TBN, phosphorus, zinc, etc, etc. You put in the best base oil, say a Group IV PAO synthetic, without any additive package, and it will destroy and engine faster than a conventional with a strong additive package. The additive package is what makes an oil meet the specs and motors that it is developed for. The base oil is just the starting point.

About the only appreciable thing that the highest class synthetics can lay claim to is their NOACK, or burn off rate, which is lower than conventional oils. But that gap has closed dramatically the last few years. Shell's oil derived from natural gas now has virtually the same low NOACK qualities of the best PAO synthetic. And the blends are typically within 1 or 2 points of it also. The Schaeffer blend I use has a NOACK of 11%. The full synthetic variety has a NOACK of 10.3. Barely a blip on the radar in NOACK difference.

And cold pour points? A typical full synthetic 5w30 has a pour point down to around -45F. Impressive. The 10w30 syn blend I use has a pour point down to -39F. Do you actually think 6 degrees difference is that major of an issue when we are talking about those kinds of temps? When temps get that low, the conventional will be like grease, but the blends and the synthetics, both, will be like molasses. At that point, oil pan warmers are essential for both to get a motor proper lubrication at start up on a cold morning. Probably why I am fond of oil pan warmers and use them!

 

Your explanation sounds very logical, but there are two things. One is, the remaining TBN was slightly lower after 25,000 miles with the Delvac 10w30 blend, 3.8, than after 40,000 miles on the Delvac 5w30 full synthetic 4.1. So, I am not convinced they use the same or, and same quantity additives. The other thing is the smoother running engine. You can say it is just an illusion, but I did not expect it at all. It was just a surprise when I started up the engine. This was the moment when I decided if it is so obvious to my ears it must be a difference for the engine too, and I will not put anything else into it.

 

Many things can affect TBN depletion. Per Mobil's site and their technical data sheets on the oils you mentioned.....

Mobil Delvac Elite 10w30 synthetic blend... TBN 10.7

https://mobildelvac.com/en/engine-oils/mobil-delvac/mobil-delvac-elite

Mobil Delvac 1 5w30 full synthetic... TBN 10

https://mobildelvac.com/en/engine-oils/mobil-delvac-1/mobil-delvac-1-le

What a person's end result is depends on so many factors including ambient operating temperatures, quality of fuel, and the list goes on and on. TBN controls acids in the engine. Those come from combustion and any anomalies surrounding that. But just from Mobil's own website, they have slightly higher starting TBN for their syn blend 10w30 compared to their 5w30 full syn. So while I might have been a little wrong on the actual add pack numbers, it was in the opposite direction... the blend has a higher TBN than the full syn.

Look it up on Mobil's website.

The differences you notice in end result TBN are not conclusive of anything. It takes dozens of test results to confirm a particular pattern. One or two do not. This is why even the oil sample folks recommend regular oil sampling to track trends and patterns. The variables that you operated the motor in between one oil and the other can affect the end result.

Cannot dispute "smoothness" feeling, as it is a feeling. Actual numbers on a sheet are the only thing that really matters in the final analysis. How does the various wear numbers compare between the two? What what the cumulative miles on the engine at each test period you mention?

 

So what is the difference between Delvac's 10w30 super and 10w30 Elite? Other than the Elite is the synthetic blend.

 

Not much. The Elite has a little lower cold flow point. The viscosity index is pretty close between the Super, Elite, and Delvac 1. It goes to what I have contended all along, modern base oils, the gap in difference between them is getting narrower and narrower. There are the more extreme instances where a synthetic or blend will offer a little better performance than the Super, but most folks do not experience those extremes. If I was operating in some pretty extreme cold frequently, the Delvac or Elite would be a better choice just because of lower cold flow.

Compare the numbers on the Super at this link and compare to the Elite and Delvac links I posted previously. Not that big of an extreme between them.

https://mobildelvac.com/en/engine-oils/mobil-delvac/mobil-delvac-1300-super

To be fair, synthetics do offer some advantage in oxidation control and thermal breakdown. That is why a blend is the most cost effective solution. It offers the best of both worlds at a very reasonable cost compared to full synthetics.

I suppose one can spend their money how they see fit on whatever helps them sleep at night. The only key thing to keep in mind, is that one should make any decision based on reliable researched information and not on glossy marketing brochures or radio talk shows. The oil companies have no problem promoting higher priced products, as they make a lot more from them. No different than most other businesses who sell stuff.

 

If I would be Schneider's maintenance manager, I would happily play around the numbers and options. However I own one truck and I sleep well if I somewhat exceed the requirements on lubrication. Maybe I waste a few hundred dollars per year, but maybe not and recoup that money multiple times in the long run. No one will know for sure, but I am fine with.
Btw, thank you for the well detailed informative post.

 

Has anybody had issues with their average fuel economy screen on the digital display going haywire? This it the Second 680 that I have had where it's screwed up. This truck is a '16, and it worked fine until I took it to KW. Now, it just reads 0.0 mpg's, and the blue line jumps back and forth rapidly. If I reset the odometer, it works fine, but as soon as I shut off the truck and start it again, it goes back to having a seizure.

Any thoughts??