[bismic]

Here is a chart that shows the Kinematic viscosity of oils at temperatures above 100*c (above 212*F). My assumption is that oil can fairly easily get to 275*F (135*C) inside the engine. Unfortunately the web site I am using for these graphs does not have a 0W40 in their chart. Anyway, please note at 135*C, the 5W40 oil is slightly higher in viscosity than the 15W40 oil.

Again though, there is definitely variability in different brands of oil!

Here is a interesting (complicated) article on shearing:

Infineum Insight - Shear stability up close

Careful evaluation of lubricant shear stability is essential to ensure lower viscosity oils offer sufficient protection to heavy-duty diesel engines. Isabella Goldmints, Infineum Lead Scientist in the viscosity modifier area, describes some of the work being undertaken to explore the viscosity...

www.infineuminsight.com

 

[Jeff-F350]

I remember going through all this yrs ago. I’m not a fluid dynamics engineer, just had cold starting issues and wanted to make things easier.

I started using 0/40 for cold temps. Night and day difference in starting close to -40 and colder. I’ve been using 0/40 and 5/40 rt6 for years in a few engines. Never had an issue. Sometimes 0/40 in summer with oci, not often, working it.

Next oil sample I send in will be 0/40 rt6. I’ll try to remember to post up the results when I get it back and mileage on it if anyone is interested. It’ll be awhile.

Interesting Jetjock’s note on the 10/30 vs 20/50.

 

[anyoceans]

Where are you located? You got some advice to use 0W40 oil. That was bad advice. It is too thin for 6.0
1. Change oil at 5,000 mile intervals religiously.
2. Ford recommends 15W40 that matches Ford specification WSS-M2C171-D, CI-4/SL, DHD-1. Part #XO-15W40-QSD or XO-10W30-QSD Don't go below 10W30. Engine bearings are expensive to replace. If you are up north get a block heater. Here in South Texas the cold oil viscosity is not important.
3. NEVER change the coolant to anything other than Ford Premium Gold. It is pricey but anything else will corrode holes in your oil cooler which puts oil in the cooling system. That is a royal pain to repair. Not a good thing. Ford Spec WSS-M97B51-A1, Part# VC-7-A
4. There are 2 different oil filters in the marketplace. Some aftermarket ones are taller and come with a taller cap. Using a FOMCO filter with an aftermarket cap allows oil to bypass the filter.
5. Your FICM voltage is within spec. If you have a hard-starting problem the first thing to look at are the plugs in the back of the FICM. The plastic clips that hold the plugs in have a tendency to break down in the heat of the engine compartment.
6. Speaking of heat - excessive idling damages the wiring on top of the engine, especially the injector wiring harness due to excess heat. Idling is not good for the life of the oil either.
7. I see you have a glow plug out. Not a problem if it starts. That cylinder may not kick off right away but will pick up when the engine warms for a few minutes. They are a pain to change. Here in South Texas we hardly ever need to use glow plugs. My wait to start light hardly ever came on.
8. I installed a Atoto A6 head unit in '03. It worked well.
You can download an owner's manual and the diesel supplement from Ford if you don't have them.

It’s all about the ambient temperature. The trucks going to start regardless of what oil you have yet if the high weight oil isn’t flowing until the engine temperature rises, that’s just wearing out your engine. 0w-40 or 5w-40 for Alaska in my area based on low (-) temperatures and mild high temperatures that rarely clear the 70’sF. There’s a reason we have multi weight oils. If you never see cool or cold temperatures, you could use a single weight (when I lived in Panama).

 

[rbraeking@gmail.com]

Wow - these are going to be never ending myths.

A 0W40 is a 40 weight oil. It is NOT TOO THIN. Ford even has multiple 0W40 oils on their approved list. Ford does not "simply recommend 15W40 oil". Ford OBVIOUSLY sells 5W40 oil, and the 6.0L owners manuals were revised to include the recommendation of it AFTER they came out with their own 5W40 oil (MANY years ago). When an engine is up to temperature, 0w40, 5W40, and 15W40 are ALL 40 weight oils. At ambient temperatures (lets just say at 0*F for simplicity, lol) a 5W40 oil is thicker than a 15W40 oil is at engine temperatures, so it will CLEARLY protect just fine cold or hot. It is the way VII additives work and the chemistry/technology behind multi-viscosity oils.

No doubt that a multi-viscosity oil with a wide split between the viscosity ratings (like 0W40 and 5W40) will definitely be a bit more prone to shearing - as the additives see heat and mechanical "wear". I would recommend some oil analyses if ever planning on running over 5000 miles OCI's. My oil change interval on 5W40 oil in Texas is around 7000 miles. I am doing well with it, but I am not "advocating" above 5000 miles.

The latest chart in a 2010 6.0L owners manual (E-series):

https://cimg5.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/625x490/80-picture_php_pictureid_81715_0b63758b8aabdbe1e46bca0c7de70e1087a416e2.jpg

Links to Fords literature on oil approvals:

FCSD Chemicals and Lubricants

www.fcsdchemicalsandlubricants.com

https://www.fcsdchemicalsandlubricants.com/additionalinfo/dieseloilsWSSM2C171F1.pdf

Still advocating Ford Gold coolant is simply crazy. A Diesel rated (for example EC-1 rated) ELC coolant is far superior to the Ford Gold. Many choices for a good EC-1 rated ELC coolant also! "Corroding holes in the oil cooler", lol! The Ford Gold coolant dropped out solids and plugged up oil coolers. Failure of these coolers came most likely from mechanical stress from poor heat/temperature profiles, and poorly understood expansion forces.

Statements from a knowledgeable Ford employee that was on the 6.0L forums in the early days:

If you're looking for a very robust, maintenance-free coolant, then I would recommend any heavy duty ELC over the Gold. HD ELC's have many advantages and they are made specifically for diesels. There are lots of name brands and off-brands.

International, who made the engine and who's engine Ford designed your cooling system around, recommends their Fleetrite brand ELC, which is currently the same exact coolant as Shell Rotella ELC. Your International dealer will carry it. They also approved the Texaco ELC. CAT ELC, Mobil/Delvac ELC, Prestone Heavy Duty ELC, Zerex Extreme Heavy Duty, Chevron ELC, etc. are all excellent. The new Delo ELC is probably the best going...8-year/750K mile interval. 1M mile interval with an extender.
Be careful some ELC coolants are not rated for Diesels, it must be a Heavy Duty ELC coolant rated for Diesels!

My recommendation is to NOT contaminate Ford Gold® with any other coolant. Obviously the OP had Ford Gold® in his system.

The OP said that he was a newbie. Sticking with the OEM recommendations is best for him. Your being a highly skilled and well trained professional engineer/mechanic gives you a little personal leeway.

 

[bismic]

Wise words for folks that choose to use Ford Gold coolant - you had better make sure that it is not mixed with anything else. In fact, even when/if you read that there is a minimal amount of mixing that can be tolerated, avoiding it altogether (if possible) is best.

Just an added comment on Gold coolant for the OP. I have run Rotella ELC Ultra coolant in my 6.0L for the last 140k miles (about 12 years). Never had a plugged oil cooler, and oil and coolant temps are still the same as when it was new (at 245k miles now). Anyway, it is Gold colored, looks just like the Ford Gold. Point being that going solely by color is not always the best way to discern what you have. It is helpful, but not necessarily a way to be 100% sure!!

 

[SuperDave23]

Just switched my truck back to 5W-40. Had been running 15W-40 since during COVID it was really hard to get 5W-40 and I rarely park my truck overnight outside in the cold. Even at 50F oil temp from sitting in the garage overnight it starts WAY smoother than the 15W-40 and that was running Delvac Extreme Synthetic. The injectors are much happier.

Did one cold start on the 15W-40 out in the desert over New Years at around 30F EOT and I'm pretty sure I was down an injector for a few seconds, truck started VERY rough, smoked, etc.

Highly recommend 5W-40.

Note my FICM is an original 2006 non-inductive heating tune. When I had it repaired by CircuitBoardMedics I decided to leave it. Didn't like the idea of running a bunch of extra amps thru the FICM every time it starts and the fact that I'm rarely starting it really cold.

 

[anyoceans]

The problem of 0W40 oil is the viscosity at low temperatures. The babbitt bearings retain a film of oil. When the temperature drops in the engine block viscosity shifts. If the engine is not designed for such a light oil the bearings may lose some of their residual oil causing a dry start. There are only so many dry starts an engine can tolerate. An engine with 100,000 miles on it already has had some bearing wear which makes 0W oil more problematic. If you can obtain an owner's manual specific to your year model, you will know for sure what oil to use.

0W oils were developed for better fuel economy. When Pennzoil was asked if a lighter viscosity oil than recommended be used, they answered: "No, if your owner’s manual calls for a thicker oil, you should not use a thinner SAE grade nor use a thicker oil for a recommended thinner oil vis-grade. Using the proper viscosity motor oil will help protect and maintain the performance of your vehicle’s engine."

I would not use anything not recommended, especially in an older engine, without advice from an engineer who specializes in lubrication technology. Advice from the interwebs that is contrary to recommendations is suspect.

The purpose for the 0w or 5w is it will flow at the low temperatures Ensuring the bearings receive oil ant the start and not relying on a residual film from the last operation until the 40 warms up.

 

[rbraeking@gmail.com]

The purpose for the 0w or 5w is it will flow at the low temperatures Ensuring the bearings receive oil ant the start and not relying on a residual film from the last operation until the 40 warms up.

I understand that is the theory, but it is not backed up by engineering data. It is only a matter of opinion. Without engineering data, I would not recommend it, especially if normal engine temperature at startup is above -15°F.

 

[bismic]

Without engineering data - lol ..... Those darn lubrication engineers just can't seem to find time to get data on diesel engines and oil ......

You can't seem to process the engineering data already posted!

To ANY other reader here - please do NOT think you should use 15W40 oil even below 20 degrees F ambient in a 6.0L!!! -15*F, LOL Even Ford shows that it isn't recommended!

Even Ford calls the 5W40 oil a "heavier SAE oil" in the 3 most current 6.0L diesel supplements, page 46, supplement attached below, pic of the page inserted below, (HEAVIER SAE 15W40 and 5W40 recommended for heavy duty driving and towing)!

 

[wpg_f250]

Without engineering data - lol ..... Those darn lubrication engineers just can't seem to find time to get data on diesel engines......

You can't seem to process the engineering data already posted!

To ANY other reader here - please do NOT think you should use 15W40 oil even below 20 degrees F ambient in a 6.0L!!! -15*F, LOL Even Ford shows that it isn't recommended!

Even Ford calls the 5W40 oil a "heavier SAE oil" in the 3 most current 6.0L diesel supplements, page 46, supplement attached below, pic of the page inserted below, (HEAVIER SAE 15W40 and 5W40 recommended for heavy duty driving and towing)!

View attachment 801997

At this point I think dude is just trolling you Bis!

 

[bismic]

LOL - he has a history of this and similar thought processes .............

You should see some of the oil forums when newbies post ridiculous stuff. They get blown out of the water quickly!! Then many seem to go to the diesel forums ......

 

[jetjock15]

I understand that is the theory, but it is not backed up by engineering data. It is only a matter of opinion. Without engineering data, I would not recommend it, especially if normal engine temperature at startup is above -15°F.

You are joking right? Just checking, even humor and sarcasm can be hard to gauge on here. If your serious… wow.

 

[Kaakau620]

What I think of when I see oil debates -

 

[wpg_f250]

What I think of when I see oil debates -

That's some flux capacitor sheet right there lol 😆