That's exactly what I've learned about Mobil 1 5W-30. It starts out on the 'thin' side of the 30 weight scale and in some cases, shears down to 20 weight after use . Actually, shearing down to a 20 weight seems to be fairly common for some 5W-30's.

 

When you say shear's down, is that in the process of making it or after use in the engine?

 

Most dino 5w30 oils and many 10w30 oils will "shear" under use in the engine. At the end of use, the oil no longer has the viscosity it originally had when you put it in.

So whats the difference: Use a 5w30 that nearly always shears to a 5w20 oil at the end of an interval, or use a more shear stable 5w20 that maintains grade over the interval.

 

Gopher is a pretty knowledgable guy.

Mobil 1 has a better resistance to shearing even at extended intervals. Synthetic hold up one heck of a lot better in these situations.


If 5W30 shears so noticably to a 5W20 weight, what about 5W20? What does 5W20 shear down to?

 

That's interesting, question for you. How long is the interval? For example I change mine at 3,000 miles, so are you saying that the 5W-30 I use would shear down to a 5W-20 in as little as 3,000 miles?

 

mf150,
5W-20 seems to stay in grade from the analysis I've seen.

01 XLT Sport,
Some 5W-30's shear to a 20 weight at 3,000 miles and others don't. 10W-30 and 5W-20 on average seem to be more shear stable than 5W-30. I believe it has to do, at least in part, with the increased amount of viscosity modifiers needed for 5W-30. Seems more viscosity modifiers can relate to less shear stability.

Gopher,
Please correct me if I’m wrong.

 

That is true from what I have heard. More polymers, more shearing. But, in the case of synthetics like Mobil 1, you rarely see that at 3,000 mile intervals.

Also, I believe the benifits of running 5W30 outweight the risks of running a good 5W20 to its max.

 

Ok, next question. What do you think of durablends? I use and have used for a long time Valvoline Durablend 5W-30.

 

I've never run a blended oil besides Motorcraft. I figure Blends are a more expensive group III lubricant, but as far as protection, I really can't say.

 

Talked to a guy from Amsoil and they sware by their new 2000 0W30 synthetic in applications that call for 5W20 or 30. Has anyone had experience with it?

http://www.amsoil.com/products/tso.html

 

I watch these 5w-20 vs. 5w-30 threads with some interest since
I recently bought a new F150 and I'm going back and forth about
which oil to use. I do have a question that I haven't seen
addressed as of yet. Ford says to use an oil that meets their
WSS-M2C-153H spec. From what I've seen this is a pretty
stringent spec, double test durations,etc. I would asssume that
there is some amount of additional chemistry to meet this spec.
Oils that meet this spec are supposed to keep engines cleaner
and do not break down as easily. Sounds like a good thing...
Maybe the 5w-20 oils are actually better for my engine than the
5w-30? At first I was dead against the 5w-20, but now I'm not
so sure.
Is this spec requirement a potential loophole for Ford to deny warranty claims?
I'm not so concerned about grade since Mobil 1 is a thin
30, just over a 20, and the Motorcraft is a heavy 20, almost a 30.
Right now I am running Royal Purple 5w-20, but I think that
might be overkill for me.
So, what is the thinking regarding the 153H spec???

Thanks

 

After 52,000 miles of using Motorcraft Oil at 3,000 mile intervals, I switched to Amsoil 0W30 and Hastings Oil Filter. The reason was the 35,000 or 1-year oil change interval Amsoil recommends. The filters are changed at 12,500 miles, with a quart of oil added, of course. This saves a lot of $$$, offsetting the $8-per-quart price of the Amsoil product. The F150 4.6 liter truck had been using oil with the Motorcraft, about a quart per 1000 miles. Now it is not using any oil. I use Amsoil ATF in the Transmission too, after 2 flushes with Ford Mercon 5, and in the Rear End, the Amsoil Series 2000 75W-140. Amsoil publishes a limited warranty, and will back up their product in writing. I pull a travel trailer, over mountain passes, so the extra quality of the oil provides a nice margin for an engine used that hard. The truck now has 83,000 miles on it.

 

Yep, some dino 5w30 oils shear to a 5w20 in as little as 3000 miles, and so do some 10w30 oils under some conditions. It depends on the oil and the driving conditions, but it is very common. Most synthetics seem to be much more shear stable than dino oils, but not all. Again, it depends on a lot of variables.

As far as the 5w20 oils shearing, yes, they still do so some too, but based on the results I've seen to date, it is much less than we see out of the 5w30 oils. They have all stayed in the 20 weight range throughout the interval, anywhere from 2500 miles to 7500 miles. Much more stable, as they should be, given lower difference in viscosites, and more stringent tests they must pass.

As to the blends, they are good and bad. I've used Valvoline Durablend for basically the entire life of my two trucks. Wear levels are excellent in both. Just beware that the "synthetic" content is usally very low in these oils, often 10%. Weigh that against the price. In any case, they are at least as good as the same brands dino oils, and generally are better. In the durablend case it is actually mostly a group III basestock with some group I or II dino. Actually a pretty good deal.

Not a very clear answer, but there isn't a great answer to that question!

dsp, as far as that being a loophole to deny warranty coverage, yes, it could be used in that manner. Likely? Probably not. We all know a 5w30 is fine in these motors. Some dealers still use just that. Just stay on the good side of your service guys and there shouldn't be an issue, but it is something to keep in mind. Only you can decide if thats important or not.

 

In addition to the previous post, at 83,000 miles the F150, 4.6, 3.55 Limited Slip, Trailer Towing, is getting 18mpg, with no trailer, highway driving. I might mention that I add RXP, (I think that's what it is called), orange bottle, white cap, to the gas tank once in a while. It is supposed to help with carbon build up. And I use EssentialLube, by Hydrotex in the gas, (1 quart to a tankfull), periodically, and a small amount in the transmission too, and sometimes I use Synergyn Oil treatment. I can't tell if any of this stuff works, but I am getting 18 mpg, highway, if the engine is under 2000 RPM. I've pulled the trailer from TX to Calif., etc. at least 10,000 miles total, with no problems whatsoever, so far.....

 

I'd actually recommend a stronger approach. If there's even a hint of warranty denial at your current service department regarding using say a good oil (other than 5w20) at regualr intervals, go find a new service department. Don't accept this sort of nonsense, you deserve better.

-Mike-