Nah. They would still say no, because I don't think Ford ever updated the oil spec. All a dealer monkey will be able to tell you is what Mommy Ford allows them to say. And that would be that the 7.3L powerstroke requires 15w40. The 5w40 is likely for the 6.7L
They tend to treat any off-spec ( according to Ford) parts/fluids as blasphemous and wholly unacceptable.

 

I could be wrong, but I think you have that backwards. Otherwise shearing wouldn't be nearly as much of an issue. I believe that the base stock starts out at the lower/"thinner" number, and then viscosity improvers are added so that as they heat up, the molecules change shape and make the oil "thicker"/more viscous. So, once the "additive package" ( or specifically the V.I.) is "used up", the oil would tend to revert to its lower viscosity / "thinner" state.
Maybe "F250" could clarify/explain?

As for my personal experience, I started using the 5w40 Rotella T6 shortly after I got my truck ( Nov. 2014). It definitely helped with cold starts in winter; especially since I had 2 bad batteries. I have run nothing but that until part way through this summer, when I switched back to the 15w40 T5.
Here's why.
I noticed that once the truck was hot, and particularly after hard driving ( long highway runs at 2500-2700 rpm and/or repeated stop light to light "racing"), the truck would idle like crap. I also noticed that as I approached the 3k mark, the idle quality got even worse. I was also getting more smoke ( lower ICP, less atomization??)
Now, I also have/had pretty decent oil leaks. While it is now a little less, I was losing 2 quarts every 1,000 miles. So, the oil would have gotten 6 quarts replenished by that 3k mark. That's more the 1/3 the total volume. So V.I./additive depletion shouldn't have been an issue. Because of this, I was doing 6k oil changes. At the 3k mark, I would change the filter (which adds another 2 quarts of replaced oil).I have since cut my oil loss in half, down to about 1 quart every 1k miles. I think the extended drain intervals, along with the summer heat, were just too much for the 5w40. It had just sheared down too much.
Since switching back to the 15w40, the truck runs smoother, longer. It feels like it is running a little stronger and smoking less. I will stick with the 15w40 for at least 1 more oil change, and then maybe go back to the 5w40 for the winter, once the temps drop.

 

It was my understanding that the wider the difference in the cold/hot viscosity, the less "stable" the oil was and much more susceptible to shear. The reason being that such an oil would have more V.I. additives (which can break down) added to a lower viscosity base stock, vs a narrow range oil.
Any comments/info?

 

I called and insisted that they use 5w-40 and Momma Ford says no and the are a perfect child. The refuse to put anything else then spec, they say it is a "Liability" and I should not trust the sources that tell me that 5w-40 is good. I cancelled for 2 reasons, 1 they would not even consider using it (would not even quote me) 2. If found that Costco has a sale on DELO 15w-40 for $31/a case so I'm gonna stock up.
I plugged in my block heater last night and she fired up like a dream, no smoke at all, so I'll probably keep using that until I am mentally prepared for a $100 oil change.

 

I run 15w40 and change every 3000 miles. i think I just like changing oil tho. I started the t6 a year ago and realized every 5000 wasn't enough to satisfy my oil changing needs. I too went from synthetic to non synthetic. My truck runs better than ever, honestly cold starts aren't that much different.

 

What's your definition of a cold start?

 

Nope. Ford started selling the 5w40 synthetic long before the 6.7 came out. IIRC, it first hit the shelves even before the 6.4 came out in 2008.
EDIT... the first post I can find here in FTE about the Motorcraft 5w40 synthetic oil being on the market was in early January 2008. It was driven by the new (at that time) CJ-4 specification standards, and coincided with the entrance of the 6.4L engine.

Just as a side note, the CJ-4 specification standard is backward compatible for the earlier diesel oil specification requirements. That means that it absolutely IS acceptable for use in our 7.3's just like current CJ-4 15w40 oils.



Shear happens in all fluids, and we all know that our Ford HEUI injection system is notoriously worse than others for dropping oil viscosity.

If you're making a comparison of "dino" base stocks for a 5w versus a 15w starting point, you have a valid point regarding the potential impact of Viscosity Improvers. However, we're talking about synthetic 5w versus dino 15w, and that is a completely different comparison.

When you look at the molecular chain lengths in a dino oil, you end up with a typical bell curve for frequency distribution (range of shorter and longer chain lengths being pretty well centered around the average chain length). You have the same type of bell curve for synthetics, EXCEPT... the process of manufacturing synthetic oils results in much narrower range of molecular lengths on a much more consistent basis, and that is true across the full range of weights manufactured as synthetic oils.

Even then, due to manufacturing differences, some synthetics are less sensitive to a shear-reduced viscosity than others, and it depends on the range of molecular chain lengths in the base oil. Those with a wider range of chain lengths will rely more heavily on Viscosity Improvers than those who start out with a higher quality base stock with a narrower range of chain lengths.

The reason for the last statement is that shear first begins to take place on the longer chain lengths in whichever oil you're speaking about. The longer the chain length, the more "sensitive" that chain is to being sheared, or broken. Consequently, just on a mathematical basis, if you expose an oil with a wide range of chain lengths to shear conditions, it's longer chains are going to get broken more quickly and then rapidly increase the already present population of very short chain lengths, and you end up with a sheared (reduced) viscosity much more quickly. In that sense, shear also takes place in a synthetic oil, but the starting point is a fluid with fewer shear sensitive long chains, so you end up with the following "advantages" with the synthetic option.

a) a less sensitive base stock which takes longer to shear, and
b) "a" above requires less dependence on VI additives, and
c) "a" and "b" lead to a more viscosity-stable product for your customer.

In my trucks, I did some initial testing with Blackstone, OilGuard, and Schaeffer on redundant samples for both brand new and used oil at various mileages. I even ran a brand comparison between Schaeffer and Amsoil synthetic 5w40 oils. I saw the Amsoil shear from a 40 weight down to a 30 weight in about 8K miles, but I easily got an EXTRA 7-9K miles (total of 15K-18K mile OCI's) from the Schaeffer before seeing it drop to a 30 weight viscosity. I was running my existing bypass filtration system for those comparisons, too.

 

When the truck has lost all of it's residual engine-produced heat due to sitting. Usually occurs overnight, but it can happen during the day if it is cold enough and long enough.

When I started my truck this morning with the help of the block heater the temp gauge was already showing a fair amount of heat. It was the best "Cold" start I've ever had, even though it really was not "cold". Temp was about 45° and I waited until the WTS light turned off, Fired up no problem and NO SMOKE!!!
Like I said gonna stick with Conventional Delo 15w-40 because of the amazing price. Maybe next change will be with synthetic...

 

Probably not the same as yours. I mean I'm talking Oklahoma winters and Salt Lake City. I've never been anywhere I've had to use anti-gel or block heaters or where 5w40 is night and day

 

in the depths of despair of winter I have not seen it go below 25° normal wintertime here is just 9 months of rain 35° and up

 

You'll be much more prepared to spend that $100 on an oil change when you see your electric bill jump $200 in a month just because you'll be plugging the truck in every night....
5w-40 your truck will thank you trust all of is here we know what we're talking about.
During the cold months I run 5w-40 and once temps hit a consistent 45+ degrees in the morning I switch back to 15w-40. Then again my Cummins doesn't really care what kind of oil is in it but my old 7.3 would throw a fit! It would pour white smoke out of the tailpipe pipe and ROMP like hell!

 

I doubt it would jump that much, IIRC the heater is a 1000W heater, this equates to 1kWH of electricity use for every hour it is plugged in. I think I currently get charged 11 cents a kilowatt hour, so for an 8 hour night plugged in it would cost me 88 cents, multiply that out over the days of the month and I should be less than $30 extra on my electric bill for the month.

Now if the OP lives in CA I could maybe see that much of a hike in their energy bill (he he he!)

 

Just use a timer

 

I know my electric bill shoots up whenever I used it consistently. Since we all know what a difference the oil can really make and not needing to plug the truck in and going by your math then after a month of not having to plug it in spending the extra $30 on an oil change pays for itself over and over. Obviously based off of how often it's used and miles driven a month would come into play

It's a pick your poison situation. Spend more up front or more later. I'm in michigan and it gets cold here during the winter and stays that way until spring

A timer like dude ford said is another good option but in all reality just switching the weight of the oil is the most feasible option

 

I know one thing......when it's cold 10 degrees or less the entire injection system will live longer and your batteries survive the cold far better with 5w-40 synthetic vs the Dino oil........when it's cd