5w-40 vs. 15w-40 the real truth?

[Gokhan]

Originally Posted By: 2015_PSD
So how much thinner is 5W-40 versus 15w40 (honest question)? It is 1.1KV difference so what does that equate to? I am not sure that I agree that a 5W-40 will cause more wear than a 15w40--why do you think this?

It's not just the KV100. Since 5W-40 has a lot more VII, its HTHSV will be a lot less because of the temporary shear of VII. (We are talking about temporary VII shear in new oil, not permanent VII shear in used oil.) For example, for Mobil Delvac 1300 Super 15w40 and Mobil 1 Turbo Diesel Truck 5W-40, you are looking at 4.3 cP vs. 3.8 cP, respectively -- a big difference as far as HTHSV is concerned.

https://www.oronite.com/paratone/shearloss.aspx

 

[mbacfp]

Excellent Gokhan. That is what I was trying to understand. I guess it is all about finding the right balance in any one type of oil type. I appreciate the education.

 

[Garak]

I believe when you're looking at Mobil Delvac 1 ESP 5w-40, you're a little closer to 4.0 or 4.1 when it comes to HTHS. It's no longer the same product as Mobil 1 Turbo Diesel Truck, as used to be the case. Also, given the builder approvals (and the price up here, at least), I would prefer the Delvac 1 ESP 5w-40 to the Mobil 1 Turbo Diesel Truck.

 

[UNC151]

Originally Posted By: Garak
I believe when you're looking at Mobil Delvac 1 ESP 5w-40, you're a little closer to 4.0 or 4.1 when it comes to HTHS. It's no longer the same product as Mobil 1 Turbo Diesel Truck, as used to be the case. Also, given the builder approvals (and the price up here, at least), I would prefer the Delvac 1 ESP 5w-40 to the Mobil 1 Turbo Diesel Truck.
I was about to say something similar so thanks for posting this. I find it hard to believe that a conventional HDEO is that much better (if at all) than a synthetic HDEO.

 

[BrocLuno]

There is nothing wrong with dino based oil if it is well refined and blended. The first and second 1M mile motors were on Delo400 and Delvac (not a synthetic), so you know that fleet oils will protect your motor. If they didn't, and there were any provable oil related engine failures for say UPS or some other big fleet operator, we all know about it... There aren't.

The refiners know what they are doing, especially the big boys. The sell zillions of gallons of this stuff and they have tens of thousands of fleet oil tests to refer to. The oil does not fail if kept within it's design envelope.

Your motor would be fine on any of these, but I'd run Delo400 or Delvac and a premium filter and do just what you are doing - change it once a year.

I don't like the drain-off problems with lower surface tension of pure synthetics. Especially when we know that your rig does not get started every day. Conventional oils may cushion better after sitting for longer periods with better capillary fill due to the higher surface tension.

It's dry starts that will harm you motor before the pumped oil gets circulated ...

 

[Gokhan]

Originally Posted By: Garak
I believe when you're looking at Mobil Delvac 1 ESP 5w-40, you're a little closer to 4.0 or 4.1 when it comes to HTHS. It's no longer the same product as Mobil 1 Turbo Diesel Truck, as used to be the case. Also, given the builder approvals (and the price up here, at least), I would prefer the Delvac 1 ESP 5w-40 to the Mobil 1 Turbo Diesel Truck.

Given that they are both Group III, have similar KV100 and VI, I doubt their HTHSVs are different. Also, don't forget that the main reason they make 5W-40 HDEO is to improve the fuel economy; therefore, they want to keep the HTHSV on the low side, slightly higher than the 3.5 cP minimum and no more than about 3.8 cP. However, you do get some extra assurance on wear with Delvac ESP than with Mobil 1 Turbo Diesel Truck because it carries more approvals. This is not to say that it's a better oil or actually results in less wear -- just more approvals (more tests done). Moreover, I don't like the fact that it's an ESP (low-SAPS) formula that much.

Does it make that much difference for wear in a light-duty diesel application whether the HTHSV is 4.3 cP (15W-40) or 3.8 cP (5W-40)? Probably a little if at all but not much. Also, synthetics tend to reduce wear a little for a given viscosity.

 

[Garak]

Originally Posted By: Gokhan
Given that they are both Group III, have similar KV100 and VI, I doubt their HTHSVs are different.

The Delvac 1 ESP 5w-40 is primarily PAO, with some ester. Chevron verified that in their testing, and published the results, which has been referenced here a few times, along with statements made by a certain someone here who knows exactly what he's talking about with respect to the product. As for low SAPS, several of us have been through this before a few times. It's a high TBN lube, as per the approvals it holds and ACEA sequences it meets. A low-SAPS heavy duty diesel (ACEA E7, E9) is not the same as a low-SAPS passenger car diesel lube (ACEA C sequences). Most ILSAC rated lubes have a significantly lower TBN than Delvac 1, and lower SA. As for the HTHS, that's been a reasoned guess put forward by some of us. Imperial Oil, unfortunately, hasn't told me as of yet.

Originally Posted By: 2015_PSD
I was about to say something similar so thanks for posting this. I find it hard to believe that a conventional HDEO is that much better (if at all) than a synthetic HDEO.

Of course, the only time I'd watch, aside from cost, is the builder approvals. As Solarent mentioned, there are a few 0w30 and 0w-40 HDEOs that have few, if any, formal approvals, and even some of the approved ones don't meet all the same ACEA sequences. Some have no certifications whatsoever, despite being part of a big company, and one is just relying on the reputation of the oil company, for good or bad.

 

[rslifkin]

Rotella T6 5W-40 is either 4.0 or 4.1 HTHS, from what I can find. The 5W-40s do tend to be a little thinner than the 15w40s, but for many of them, it's not a dramatic difference (and they're still plenty thick enough if the engine is also spec-ed for 10w30).

 

[mbacfp]

Thanks again for sharing all your knowledge. Holding any fuel savings and extended OCIs aside...bottom line, if operating within 15w40's temperature range it will most likely provide equal, if not more, engine protection in comparison to a 5w-40 synthetic?

Am I correct in interpreting current oil advancement (at least in this case) is moving towards maximizing fuel economy and longer drain intervals? I see a lot of research implying equal engine protection as with 15w40 and claiming they have achieved this with new formulations of 5w-40 and 10w30?

From my Ford manual on the 6.7 Powerstroke, they recommend 10w30 for normal operation, 15w40 if using biodiesel, and 5w-40 if using biodiesel and severe service conditions (towing, lots of relative idling, etc.).

However, my nearest ford fleet center in Van Nuys says they recommend 10w30 (even when explaining my application). I asked what they use for their commercial bucket work truck customers and the answer was still 10w30. Seems like the emphasis is on fuel economy savings not longevity? Or maybe not with current advancements in oil technology? Ford clearly doesn't believe 10w30 holds up to severe service, but am sure stands behind warranty claims when they run 10w30 in everything?

 

[m37charlie]

My $0.02 worth:
There are 2 good reasons to run synthetic - low temp requirements and intention of very long OCIs. Living in Calif. and owning an engine with a miniscule 5000 mile OCI requirement negate both arguments.
I'd run a good 15W40 or 10W30.
You will note from my sig that I do run synthetic in my Unimog. I live in Alaska (admittedly a relatively temperate part) and my engine allows 1200 hr (42K mi) OCI.

Charlie

 

[mbacfp]

Thanks BrocLuno, I also had concerns about the truck not running all the time. Fortunately, since it is stored at my house I am usually running it every 15 days or so (as per Fords recommendation). Can anyone explain the drain-off problems with lower surface tension of pure synthetics? Thanks again for all the discussion.

 

[mbacfp]

Thanks Charlie,

That is what my gut is telling me...leaning more towards the 15w40 vs. the 10w30...but am open to change. Just want to understand the engineering and chemistry behind the decision. Thanks.

 

[UNC151]

Originally Posted By: mbacfp
However, my nearest ford fleet center in Van Nuys says they recommend 10w30 (even when explaining my application). I asked what they use for their commercial bucket work truck customers and the answer was still 10w30. Seems like the emphasis is on fuel economy savings not longevity? Or maybe not with current advancements in oil technology? Ford clearly doesn't believe 10w30 holds up to severe service, but am sure stands behind warranty claims when they run 10w30 in everything?
My dealer recommended the same to me when I bought my 2015, but I am going to run either 5W-40 or 15w40 and leave 10w30 out of the equation. I have a two OCs remaining with 5W-40 (Rotella T6--but am currently running Delo LE 5W-40) and after that I will likely either use Delo or Rotella 15w40. Call it an "emotional" response, but a xW-30 just does not seem right in a diesel--especially ones that have a fair amount of fuel dilution--xW-40 would give you a little more "margin" to compensate for the dilution. YMMV!

 

[mbacfp]

I totally agree. Perhaps 10w30 might be fine, but...? I am currently using Valvoline Premium Blue Extreme 5w-40 and stocked up on Delvac ESP 5w-40 during their recent sale. DNewton's UOA article is an interesting read showing no noticeable wear tradeoffs even with a 10w30...so maybe I will change my way of thinking down the road. My truck is under load all the time and regens every 500 miles (per ScanGuage II), so my relative fuel dilution should be rather low. New to this site and enjoy leaning from you all.

 

[mbacfp]

A little off topic, but Cummins doesn't recommend synthetic oil for my Onan Diesel Generator. Manual states "...not recommended until after warranty." They recommend 15w40 for year round use, which I have been doing.

 

[UNC151]

Originally Posted By: mbacfp
DNewton's UOA article is an interesting read showing no noticeable wear tradeoffs even with a 10w30.
I have not read it in a while, but I wonder how many new diesels were in the data (e.g, those with SCR/DPF systems) such that fuel dilution is taken into account.

 

[mbacfp]

Good question and point. However, if not extending OCIs that should not be a problem. Yes, I would think a 10w30 in an extended OCI situation (which I doubt anyone would do with that oil) would break down faster than a 5w-40 or 15w40? Looks like using a 10w30 in our application for an appropriate OCI interval should not create any more engine wear than a 5w-40 or 15w40. The UOA data seems to back it up...so DNewton might be on to something.

 

[UNC151]

Originally Posted By: mbacfp
Good question and point. However, if not extending OCIs that should not be a problem. Yes, I would think a 10w30 in an extended OCI situation (which I doubt anyone would do with that oil) would break down faster than a 5w-40 or 15w40? Looks like using a 10w30 in our application for an appropriate OCI interval should not create any more engine wear than a 5w-40 or 15w40. The UOA data seems to back it up...so DNewton might be on to something.
I think it depends. It depends on how bad the fuel dilution is and how much time you spend idling. I am not thinking that 10w30 will cause more wear, but it seems to be somewhat of an irrelevant oil in the space between 15w40 and 5W-40 (note that I am only thinking about light diesels and not OTR)--at least it is for me; xW-40 makes more sense (no matter which flavor I choose).

 

[mbacfp]

I completely agree. That is where my current level of comfort lies at this time. Open to learning more, but for now will be sticking with the xW-40 as well. Have 2 oil changes in stock with Delvac 5w-40 ESP. How do you like the 2015 powerstroke? My father in law claims he gets better mileage than his 2014 work truck he had? He drives 1,000+ miles a month.

 

[Gokhan]

Originally Posted By: Garak
Originally Posted By: Gokhan
Given that they are both Group III, have similar KV100 and VI, I doubt their HTHSVs are different.

The Delvac 1 ESP 5w-40 is primarily PAO, with some ester. Chevron verified that in their testing, and published the results, which has been referenced here a few times, along with statements made by a certain someone here who knows exactly what he's talking about with respect to the product. As for low SAPS, several of us have been through this before a few times. It's a high TBN lube, as per the approvals it holds and ACEA sequences it meets. A low-SAPS heavy duty diesel (ACEA E7, E9) is not the same as a low-SAPS passenger car diesel lube (ACEA C sequences). Most ILSAC rated lubes have a significantly lower TBN than Delvac 1, and lower SA. As for the HTHS, that's been a reasoned guess put forward by some of us. Imperial Oil, unfortunately, hasn't told me as of yet.

If it's an all-PAO oil, it's great because it would be the only all-PAO Mobil 1 oil out there. It's surprising that they would only make an all-PAO oil for 18-wheelers and nothing else. Its pour point is very low; so, maybe it is, but I think it's more of a wishful thinking. It's very expensive and very hard to get in US. I also don't like that it doesn't have moly.

Regardless, it has a very high VII content and its HTHSV will be on the low side, probably around 3.7 - 3.8 cP. PAO base oils tend to have lower VI than Group III+; so, it doesn't help with HTHSV to have PAO, unless some mPAO HTHSV booster is used (unlikely in this case). See the test by Shell, showing that it shears a lot, more than the other popular HDEOs, indicating a high and/or not-shear-stable VII content and therefore a low HTHSV.

I think more or less all 5W-40 oils have HTHSV around 3.7 - 3.8 cP, including Rotella T6. Therefore, they are a lot thinner than 15w40. In fact, Rotella T6's KV100 is a somewhat low 14.2 cSt. This is because the main idea of 5W-40 is to improve fuel economy over 15w40. Fuel economy is very important for 18-wheelers.

All this said, in a light-duty diesel application, I would probably use Mobil 1 Turbo Diesel Truck or Rotella T6. Delvac 1 ESP is also OK if it's affordable. I wouldn't spend a fortune on it though -- after all, it doesn't even have moly.