I don’t believe I have access to “high sulfur” fuel. Is that still available in some markets?

 

No, LSD was phased out with the EPA 2007 rules and <15ppm sulphur ULSD became the standard. Ag diesel (red dyed) was available for awhile after that, but it disappeared too. Haven't seen any of it since the big 2008 price run up that I can recall, and by 2010 it wasn't being produced anymore.

That's how old these engines are now

 

(Original version, prior to bismic's subsequent edit)


The chart posted was selected based solely on the Owner's Manual of the model year (2004) shown in the profile of the original post.

Additionally, 2004 also happened to be the same model year of one of the respondents questioning the recommendation of 15W-40 during summer months.

If the OP, or any of the questioning members, had a 2008 6.4L, then the owner's manual for a 2008 would have been posted instead.

The selection of relevant Owner's Guides had nothing to do with the inapplicable accusation of "old chart is what is always drug up."

It was actually quite difficult to obtain the period correct model year Owner's Guide, since Ford just recently removed 15 model years of coverage from the Ford Owner's Manual database. 1999 - 2013 are now no longer available to download as pdfs. Which is kind of a shame.

As for the "update" in Ford's viscosity recommendations, that coincided with Ford's introduction of their own Motorcraft brand of 5W-40 synthetic (bottled by Conoco-Phillips) and coincided with Ford's introduction of an all new diesel engine in calendar year 2007 (the 6.4L)... one could argue that this chart is "outdated" as well.

But I'm not here to argue.

I'm here to recommend that anyone in southern climates take advantage of an updated availability of a full synthetic 15W-40 heavy duty diesel engine oil around 2018, which is just as significant as the update in availability of 5W-40 full synthetic from 10 years prior, in 2008.

There are good reasons why Shell spent the money recently (around 2018) to expand the viscosity offering of what was already their best selling full synthetic Rotella T6, which previously only was offered in 5W-40.

Why fix what wasn't broken? Why tweak what is working? Why invest in manufacturing, marketing, and distributing a new SKU if one doesn't have to?

The reasons are multiple, and meaningful, and they are also complex, involving fluid mechanics for the force function of the engine oil for the hydraulically driven injectors, thermal and shear stability of viscosity improvers over time and use, the chemical composition and interaction of byproducts from their breakdown... are best left up to each individual to pursue and peruse to their own satisfaction.

From time to time, as oil standards and offerings evolve over the decades, I investigate what is available for optimal use.


When Ford released the "updated" oil recommendation chart in 2007, I noticed. ("Not in time for F-series people to notice"?)

That same year, around 2007, I switched from dino 15W-40 to full synthetic 5W-40, and like you, I ran 5W-40 year round, hot summers included, for more than a decade.

I started with Rotella T, before the "T6" brand moniker was invented. Here is one of my old bottles that I saved for other uses outside:





Rotella "T" (no number) SAE 5W-40 full synthetic was so well regarded and became such a popular product for Shell during that time period, Shell decided to take advantage of the brand equity built into the Rotella T name, and started applying it to several other HDEO offerings, including less expensive non-synthetics, and synthetic blends. Hence Shell came up with a numbering system to distinguish the different Rotella T's. The full synthetic 5W-40 Rotella T was renamed to "T6".

Here's another one of my old bottles, from 11 years ago, in 2013:





And here is another bottle that I've used a lot of, although unlike the above two photos, the photo below is an image of Shell's, from 7 years ago, in 2017:




The point that my old oil bottle photos is intended to illustrate is that you are preaching to the choir here. I have used 5W-40 year round, winter and summer, in sunny and hot valleys of the west coast, for 14-15 years.

In 2018, however, I noticed that Shell introduced Rotella T6 in a 15W-40 viscosity... significantly reducing the viscosity spread in the multi-weight full synthetic oil.

Comparing these multi-weight offerings, a 40 weight isn't always a 40 weight. It is only a 40W when new. And it is only a 40W because of the viscosity improvers (VIs) that make it a 40W.

When the VIs breakdown, the oil becomes less than 40W. A 5W-40, with a 5W base oil, requires more VIs to make it a 40W. A 15W-40, with a 15W base oil, requires less VI's to make it a 40W. Less VI's to obtain 40W can mean less VI's to breakdown, which can mean less impact that a breakdown of VIs can have on the net material properties of the oil actively in service (as opposed to the oil when new).

The breakdown of any additives in an oil can leave byproducts that have unfavorable characteristics... another reason to change the oil eventually, no matter how well filtered with bypass filters, etc.

I had a lot of inventory remaining of 5W-40 T6, which I purchased at time of sale, rather than at time of need. I also didn't mind waiting a couple of years after a new product is introduced in the field, to allow the early adopters to be the beta testers. Eventually, I started buying the new T6 15W-40 (in advance of the need) when found on sale (a local CarQuest was closing, and 75% off beats any of Shell's game playing rebates).

Once I started using the 15W-40 T6 (at some point after the pandemic, so maybe 2021 or 2022), I noticed an immediate difference in two areas: more responsive performance (which I attribute to the higher base viscosity and density of the hydraulic force fluid), and less oil consumption between change intervals.

If the OP lived in North Dakota, I'd probably recommend 0W-30 or whatever. But Raleigh, North Carolina has seen record ambient temps of 105°F in June, July, and August, and 104°F in September, according to NOAA weather history. If using a Super Duty for towing or hauling in temperatures like that during those months, I would highly recommend using 15W-40 during those months, and switching to 5W-40 during the winter months. If driving 10K miles per year, that would cover the two oil changes at the 5K service interval that Ford recommends for the 6.0L.

Since Ford recommends different oil change intervals for different diesel engines, the "updated" 7,500 mile oil change interval that Ford recommended for the 6.7L (before Ford added an "intelligent oil life monitor" system) would not be applicable to a 6.0L, especially because of the HEUI injection system of the 6.0L.

By anyone's account, 460,000 miles is certainly a milestone to achieve on ANY engine. I've achieved the same number of high miles in a Ford gas engine, where after about 299,999 miles, I "updated" viscosity from the original Ford recommended 5W-20... up to 5W-30, to account for what I can only imagine to be some wear on a little 4 cylinder Duratec that has never been opened, removed, or even touched internally, and have run the slightly thicker multi-weight oil for the last 160,000 miles.




Here are some interesting videos to watch on this topic.




(Long, watch at 2X speed, but relies on Oil Analysis and instrumented monitoring..."data, and not emotion, driven")

 

There is a TECHNICAL reason Ford calls 5W40 a thick oil. The reason is because it is a thick oil at the operating temperatures of the engine. SAE J300 specifically shows that it is a 40 weight oil - period!



Ford recommends it for towing and heavy duty applications, because it is designed for it - they documented it.

I also have plenty of data showing that 5W40 oil will stay in the 40 weight viscosity range at 5000 mile intervals. I have posted it plenty of times before. I did agree (and posted such) that 15W40 will shear more slowly (5W40 shears more rapidly), but 15W40 still shears. The technical side of shearing has been discussed many times - it is really about shearing rate because we know that ALL multi-viscosity oils will shear. The UOA data (and I have plenty) is what proves the point about the shearing rate - not perceived responsiveness or the like.

You keep calling it a 6.4L manual because you are being stubborn on that. The manual is TITLED - "E-SERIES". That is ONLY a 6.0L engine. The 6.4L was never in an E-series. Do you actually believe that Ford's Owner's Manual for the 2008-2010 E-series actually did not take into consideration the specific engine that is in it? You are grasping at straws with that argument because Ford CLEARLY intended those manuals for the 6.0L engine. And any mention of the 6.7L in this discussion is, well, not applicable. IN FACT, the 6.0L engine is SPECIFICALLY MENTIONED in the manual. I'll attach it AGAIN for interested folks. Page 20 SPECIFIES that the 6.0L engine is applicable to the manual. The oil chart is Page 46. In that chart, 5W40 is called a "Heavier" oil. (Heavier SAE 15W–40 and SAE 5W–40 engine oils are recommended for temperature over 50°F (10°C) and must be used for heavy duty driving and trailer towing.)

Ford even updated their chart for all 6.0L's, but that chart does not exist anymore because the platform is WAY OUTDATED! You imply that it never did exist, but it did.

The 2004 manual did not include 5W40 because Ford did not sell it at that time ...... period. I had this discussion w/ a person that worked for Ford. It has nothing to do with the difference between a 2004 variation of a 6.0L vs. a 2008 variation of a 6.0L (which was really just a 2006/2007 6.0L engine as @texastech_diesel pointed out). Ford updated their recommendation on their web site and I have attached the documentation. You don't believe that, but it is of no consequence, because Ford's position is clear. A 2008 and 2009 6.0L is the same engine as a 2006 engine with only a few minor "running" changes made in 2006. Ford states to use 5W40 in over 100 degree ambient temperature in the 6.0L, ALONG WITH recommending the 15W40. So no one is saying to NOT use the 15W40 in higher ambient temperatures.

Take the thick/thin discussion to BITOG and you will get the straight scoop from people in the industry. The physical properties of multi-viscosity oil are well documented. Only as an fyi - I have had more fluid dynamics education than most folks here, so IMO the Internet videos on that are of limited value.

 

Here are two charts on my 5W40 oil shearing rates. The charts show that the shearing clearly occurs (we all agree it happens). 68 SUS is still a 40 weight, so the data at 5000 miles was in spec for 40 wt (only a couple of exceptions) and not far under at 7500 OCI. Some of the 5W40 data included Archoil. The blue points are the 5W40 and the brown ones are for a 10W30. We could split hairs and say every 1.0 SUS interval is important, but 6.0L specific UOA results show that it isn't. These charts were created in a discussion with a person that claimed that 10W30 was plenty good to use in hot ambient temperatures and for towing. He still posts that (and his UOA results from his 6.0L days) over on BITOG. He implied that 10W30 didn't shear, but clearly it does.




OCI clearly means more than ambient temperature for oil service. IMO there are more important reasons not to extend OCI than viscosity shear.

 

Still waiting to hear what Mark has used in his 460k miles so I can switch to that.

 

He made his original post and hasn't logged back on since making it. We need to "tag" him.

@mmenzies00

EDIT: He has been a long time member and he had great service life with injectors also. 190k or so on the originals I believe, and then not sure after that.

 

ANYWAYS this is my second time running Delvac and went with 0w40 this time(5w40 last time i used it)and engine is quite a bit quieter, but no Archoil mixed in this time FWIW. I always run T6 0w40 or 5w40 with Archoil btw.

 

I'm at 180k on my originals. Hope I make another 100k LOL

 

245k on my originals so far.

 

Sorry guys I have been on a trip (will have done about 6K miles in about 3 weeks)and after the first couple of posts I was not notified that there were so many detailed and knowledgeable posts. I really appreciate your inputs here
I have generally used 5 W40 and 15w40 interchangeably mostly based on what is available at the time although always preferred 5 w in winter and 15w in summer. But always Rotella T6 and religiously changed at 7.5K miles. I recently had a choice of 0W 30 5W40 and 15 W 40 and thought oh dear what should I be using? So I posted here suspecting I would get some good answers.
I don’t tow but the box on the truck is pretty heavy I believe when full of fuel, water tank full and loaded with dogs it’s about 10K lbs. I don’t drive it hard or with a lead foot, but my feeling is that in summer oil temps through scan gauge seem to be higher when using 5W than when using 15W but that may not be scientific just my instinct.
sorry for late response and thanks for all your input

 

The ironic thing is that you were looking for what oil to use, and yet, with the good results you've had, many are interested in what you've used.

So it sounds like good maintenance, good oil, and running it as it was designed for. Thanks for the interesting topic.

 

Have you ever noticed a difference in MPG between 5w40 and 15w40?

 

Thanks Mark. Could you confirm your injector life/replacement history? What caused you to change out your injectors? Also, how many miles on average between oil changes - ie OCI?

Injector life is an additional "key factor" to success, (although clearly the 460k miles is the primary achievement - and a great one).

One extra variable in the mix is the fact that the CK oils have replaced CI and CJ oils. Then you have the whole Ford approval thing to think about ........ Not much long term data comparing CK and CJ oils in a 6.0L (HEUI), so many questions can still be asked!

The intent was for the CK oils to be MORE shear stable than the previous formulations, but there are still a lot of unknowns IMO. This expected shear stability should actually improve the performance of the 5W40 oil year round, but who knows specifically with a 6.0L. I have watched for good data on this, but haven't found any - not as many 6.0L enthusiasts these days. I only have a couple of runs (5k miles each) on the new CK oil, and my oil analyses results have still been as good as the previous oil.

I am at about the same vehicle weight and driving style as you. One exception is that a lot of my miles have been with a performance tune (Gearhead SRL+). Even tuned, I have always run VERY GOOD ECT and EOT. Because of that, I have little doubt that had you closely tracked the oil temperature numbers, the 5W40 would have been shown to have essentially the same oil temperature numbers as 15W40 ...... since both are 40 weight oils.

So - sounds like you should do well with the same oil change habits that you have had in the past, but my oil change data (again - mostly on CJ oils, but several with CK oil) shows that you should also have absolutely no problems w/ a 5W40 year round. Ford warned us in the early days about the lower ambient temperature issues (injector stiction) that would exist w/ 15W40. Again, maybe some of that has changed with the CK oils, but I would still not use 15W40 oil when temperatures consistently dropped below freezing because of the injectors.

 

Another thing that would be cool to see Mark is an oil analysis at your next oil change.