15w-40 in Prius

[JOD]

Originally Posted By: BillyTheKid
It will be fine. I'm even doubting noticeable mpg differences. I'd have no worry if it were mine.


When you consider than engine losses are directly related to hths, it's hard to believe that fuel economy won't be affected, unless you start violating some basic laws of thermodynamics. This oil is about 65% thicker in operation than most 20W oils. It's going to make a difference, whether people want to believe it or not.

On a car getting 20-25mph, a 3-5% loss in FE gets lost in the noise. In a car getting 50mpg? That's a different story.

 

[uart]

Originally Posted By: JOD
On a car getting 20-25mph, a 3-5% loss in FE gets lost in the noise. In a car getting 50mpg? That's a different story.


I agree JOD. I'm guessing about 2MPG, which isn't much in percentage terms, but should be enough to be noticeable by the OP. It will be interesting to see anyway, it would be nice to have at least one real world data point on this.

BTW. I've personally tried smaller variations in viscosity in my 2005 Priu. Last year I changed from Valvo Durablend dx1 (dexos1-gf5 hths=2.9) to Castrol Edge A3/B4 (acea A3/B4 hths=3.6), both oils 5w30. I tried but couldn't detect any difference in the fuel economy. The OPs change is a lot bigger though, so the change should be detectable.

 

[Shannow]

2MPG is more than 4%...way more between GF-5 performance and the "reference" 40 grade.

 

[Clevy]

Originally Posted By: JOD
Originally Posted By: friendly_jacek
Now if the OP is doing high speed hwy driving, there will be near zero MPG change. If short city trips, huge drop in MPG. This is what I saw in Subaru going from 5W30 to 5W40. Prius should not be different.

But, I would change that oil before winter for sure.


I'd expect it to make a bigger difference in a Prius than in your Subaru, since engine internal friction is a more significant portion of fuel use in a Prius than a Subaru, particularly at highway speeds; 2 drive axles, lighter weight and significantly better aerodyamics mean the engine is a bigger source of losses in the overall system (as a %). If anything, short city trips should be LESS affected than highway, particularly since he'll be on battery power more often.

Interesting if you do the maths. If he loses 2mpg over the course of a 10K OCI, the "free" oil is actually costing him about 10 bucks compared to Mobil 1 0W20.


Great analogy. Sure the oil cost the op nothing however the extra fuel burned ends up costing more than if he would have just bought the right oil.
Funny. Doesn't pay for the oil but costs more in fuel.
Doesn't sound sensible to me but that my simple opinion.

 

[Shannow]

ASSuming that the calculated 4% hit in mileage that makes the case non-sensible is actually WHAT HAPPENS in the OP case.

It's double the savings that a GF5 would make over a reference 40 grade, so 4%+ sounds nonsensical in this case.

 

[uart]

Originally Posted By: Shannow
2MPG is more than 4%...way more between GF-5 performance and the "reference" 40 grade.
Yeah I think it will depend on what type of driving the OP is doing. The prius oil is fairly slow to warm if you're only doing easy driving. That's why I think up to 2MPG is possible.

 

[Shannow]

I think some (all???) US Priuses have a thermos in their cooling system to ensure that warm-up is as quick as possible.

 

[JOD]

Originally Posted By: Shannow
2MPG is more than 4%...way more between GF-5 performance and the "reference" 40 grade.


1) The OP claims he's getting 48mpg out of his Prius, which is pretty typical. How is 2mpg "way more" than 4%

2) The reference oil isn't a 40 grade, it's a 20W30 grade with an hths of 3.6. The OP is using a diesel 5W40 with hths listed as >4.0 (at least as far as I've seen). And FE correlates mostly with hths.

Originally Posted By: Shannow
It's double the savings that a GF5 would make over a reference 40 grade, so 4%+ sounds nonsensical in this case.


Not really: http://www.swri.org/4org/d08/gastests/pdfs/ilsacGF5-7.pdf

It appears that the difference between an energy conserving 0W20 oil the reference 20W30 is closer to 6% (FEI SUM). Of course, this is in a 6 cylinder GM. I have no idea what the real-world difference will be in a Prius, but 4%, or 2mpg seems pretty reasonable to me in this instance, unless I'm missing something obvious. Does a Prius also have a regenerative engine as well, using the extra heat generated from frictional losses to charge the battery or something?

 

[Shannow]

Where do you get the 6% ?

You don't add up xW20, xW30, and 10W30...

 

[billythekid]

Originally Posted By: JOD
Originally Posted By: BillyTheKid
It will be fine. I'm even doubting noticeable mpg differences. I'd have no worry if it were mine.


When you consider than engine losses are directly related to hths, it's hard to believe that fuel economy won't be affected, unless you start violating some basic laws of thermodynamics. This oil is about 65% thicker in operation than most 20W oils. It's going to make a difference, whether people want to believe it or not.

On a car getting 20-25mph, a 3-5% loss in FE gets lost in the noise. In a car getting 50mpg? That's a different story.



My bet is in the real world the driving won't be consistent enough to prove it. Even a pretty straight commute daily can differ slightly enough to change tracking mpg. That's IMO anyway. Either way, I don't fear thicker oils. They never did my any harm in my experiences.

 

[JOD]

Originally Posted By: Shannow
Where do you get the 6% ?

You don't add up xW20, xW30, and 10W30...


uggh..I tried to copy and paste from that link: formatting nightmare!

1.5% 10W30 vs. reference oil
1.9% XW30 vs 10W30
2.6% Xw20 vs XW30

Those are the fuel economy increase sum numbers, which are a sum of the low-aged oil and the aged oil. My understanding is that they'd be additive, since they're compared to one grade down. And again, this is compared to a reference oil of hths of 3.6 or 3.7 (can't remember).

Granted, there are a lot of variables going on--this is a test on one engine. There were some "real world" test on another published API paper to validate the test results, and they seemed to show 2-5%, but with all of the typical qualifiers. I'm certainly willing to be wrong on this one, but given in information out there correlating hths to FE, I don't think 4% or 2mpg is that unreasonable based on the info out there. The old Taylor & Coy paper (hosted on Prius Chat, the google can probably find it) showed something like 5% between 5W30 and 20W50, so again, 2.6 hths vs >4.0, 4% seems reasonable. And again, engine losses are a bigger % of total losses in a reasonably light, low Cd car like the Prius.

 

[JOD]

Originally Posted By: BillyTheKid


My bet is in the real world the driving won't be consistent enough to prove it. Even a pretty straight commute daily can differ slightly enough to change tracking mpg. That's IMO anyway. Either way, I don't fear thicker oils. They never did my any harm in my experiences.


I totally agree. But again, just because the differences are tough to measure, doesn't mean they don't exist. The advantages of less frictional losses don't magically go away when the conditions change, after all.

I don't fear thicker oils, either. I seriously doubt it will have a real-world impact on the longevity of his car either way. But I do believe that it'll affect FE negatively, and probably enough to make up for the free oil.

 

[Shannow]

Originally Posted By: JOD
Originally Posted By: Shannow
Where do you get the 6% ?

You don't add up xW20, xW30, and 10W30...


uggh..I tried to copy and paste from that link: formatting nightmare!

1.5% 10W30 vs. reference oil
1.9% XW30 vs 10W30
2.6% Xw20 vs XW30

Those are the fuel economy increase sum numbers, which are a sum of the low-aged oil and the aged oil. My understanding is that they'd be additive, since they're compared to one grade down. And again, this is compared to a reference oil of hths of 3.6 or 3.7 (can't remember).

Granted, there are a lot of variables going on--this is a test on one engine. There were some "real world" test on another published API paper to validate the test results, and they seemed to show 2-5%, but with all of the typical qualifiers. I'm certainly willing to be wrong on this one, but given in information out there correlating hths to FE, I don't think 4% or 2mpg is that unreasonable based on the info out there. The old Taylor & Coy paper (hosted on Prius Chat, the google can probably find it) showed something like 5% between 5W30 and 20W50, so again, 2.6 hths vs >4.0, 4% seems reasonable. And again, engine losses are a bigger % of total losses in a reasonably light, low Cd car like the Prius.


They aren't cumulative, they are all versus the reference oil, i.e.

1.5% 10W30 vs. reference oil
1.9% XW30 vs Reference oil
2.6% Xw20 vs Reference oil

No wonder there's so many silly ideas going on if a simple chart gets so confusing.

 

[Shannow]

Originally Posted By: JOD
Originally Posted By: Shannow
2MPG is more than 4%...way more between GF-5 performance and the "reference" 40 grade.


1) The OP claims he's getting 48mpg out of his Prius, which is pretty typical. How is 2mpg "way more" than 4%


Re-read my post (in your quote) properly...

 

[JOD]

Originally Posted By: Shannow
Originally Posted By: JOD
Originally Posted By: Shannow
Where do you get the 6% ?

You don't add up xW20, xW30, and 10W30...


uggh..I tried to copy and paste from that link: formatting nightmare!

1.5% 10W30 vs. reference oil
1.9% XW30 vs 10W30
2.6% Xw20 vs XW30

Those are the fuel economy increase sum numbers, which are a sum of the low-aged oil and the aged oil. My understanding is that they'd be additive, since they're compared to one grade down. And again, this is compared to a reference oil of hths of 3.6 or 3.7 (can't remember).

Granted, there are a lot of variables going on--this is a test on one engine. There were some "real world" test on another published API paper to validate the test results, and they seemed to show 2-5%, but with all of the typical qualifiers. I'm certainly willing to be wrong on this one, but given in information out there correlating hths to FE, I don't think 4% or 2mpg is that unreasonable based on the info out there. The old Taylor & Coy paper (hosted on Prius Chat, the google can probably find it) showed something like 5% between 5W30 and 20W50, so again, 2.6 hths vs >4.0, 4% seems reasonable. And again, engine losses are a bigger % of total losses in a reasonably light, low Cd car like the Prius.


They aren't cumulative, they are all versus the reference oil, i.e.

1.5% 10W30 vs. reference oil
1.9% XW30 vs Reference oil
2.6% Xw20 vs Reference oil

No wonder there's so many silly ideas going on if a simple chart gets so confusing.


first off, the chart isn't that clear if you read the text of D7589. Secondly, even if it's not, I'm not sure why you continue to say it's a silly idea. If you're right and it's not additive, it's a 2.6% gain (at a minimum) against a reference oil that is 30W (not a 40W as you keep saying). The OP is using a diesel oil that is significantly thicker than the reference oil, and in a different car. And again, 4% IS roughly 2mpg, unless you're going to argue that, too... So again, 2mpg doesn't seem unreasonable. Whatever.

 

[Shannow]

It's actually a minimium of 1.2%, and not 2.6% (yes, against a 20W-30 reference...)
http://www.ocsoil.fi/upload/News on Lubes/ILSAC-GF-5.pdf

But like I said, 4+% is still way more than even 2.6 (which you apparently read as 4% is more than 2/48)

And yes, adding up the brackets to make 6% is just plain silly, particularly as you are so passionate about it. No sane person or oganisation would make a leap frog specification of getting to xW-20 fuel savings by progressively going a grade thinner...that misunderstanding of a fairly simple table would explain many of your views in other threads...xW-20 doesn't give you magic mileage...but if you are are a car manufacturer going for fleet averages, it's certainly in your favour.

 

[Cristobal]

When is your next anticipated oil change? It might be too thick for the winter, but if you do 70 miles per day no problem as you will change it by the time it gets really cold.

Or around 11/1/2013 dilute it a little with some MMO.

I do not think it will affect mileage all that much. Also, it will not be too thick until you get nights below freezing. Those are just my opinions though.

 

[friendly_jacek]

Was this a trolling post? The OP should have some numbers back from his MPG display, right?

 

[oggb]

No difference in MPG at this point. Prius is still reporting 48.3 MPG. I drive around 600-750 miles per week, usually 60/40 mix highway/city driving.

Next oil change will probably be in about four months assuming no long road trips. I think I have some Rotella T6 I bought for my Subaru laying around somewhere, so that'll probably get put in the sump next time 'round.

Didn't think BITOG would care about this so much. I, like many of you, am disappointed in a lack of noticeable change in MPG. Part of me really wanted the 15w40 conventional to cause a 2-3 MPG difference.

 

[Brule]

I would think loss of mpg due to thicker oil viscosity would be less noticeable in a hybrid since it would have zero effect the times the electric motor is exclusively running the car.