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#3389856 - 06/05/14 03:02 PM is 0W-20 always better for mpg than 5W-20?
Jasper8146 Offline


Registered: 04/25/10
Posts: 157
Loc: Lenexa, Kansas
I just read the Motor oil 101 to 109 here on BITOG and if I understood correctly what he was saying, it seemed to me that he was saying that all motor oils were actually too thick at room temperature to give optimal lubrication and optimal mpg at initial start up but that 0W oils were thinner than others and thus minimized the problem. So, my question is for a 2014 Kia Forte 2.0 GDI which recommends 5W-20 or 5W-30, if I'm not doing any abusive driving or high speed driving in Arizona during the summer, would 0W-20 and 0W-30 be better choices if my goal is to achieve the highest fuel economy? Am seriously thinking about the Toyota 0W-20 as it seems to have gotten rave reviews here on BITOG and other places. On the other hand, I don't want to jeopardize the warranty either, especially if using the 0W-20 is not going to make a meaningful difference in mpg. What are people's thoughts here about this? This vehicle only has 2300 miles on it and am just about to do my first oil change. Thanks in advance for the input.

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#3389864 - 06/05/14 03:15 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
4wheeldog Offline


Registered: 04/23/12
Posts: 117
Loc: East Mountains, NM
I doubt the mileage increase will be anything you could put your finger on.

We also do not know what Kia knows about 0/20 in their motors that we do not. I suspect that they just did not consider them, when making the specification, but it is a new car, and you really do not have a lot to gain but going outside the manufacturer's specs.....JMHO.

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#3389867 - 06/05/14 03:17 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
surfstar Offline


Registered: 09/16/04
Posts: 4275
Loc: Santa Barbara, CA
You'll save more money by buying 5w20 on sale, vs the gas savings obtained with 0w20.

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#3389871 - 06/05/14 03:24 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
Clevy Offline


Registered: 11/11/10
Posts: 6995
Loc: Saskatoon canada
The only difference between those 2 grades will be at start up,and only once the ambient temps get into the negatives,so for your Arizona conditions there will be no meaningful difference so pick a 5w-20 grade in the flavour you like best,or what's on sale and call er done
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#3389876 - 06/05/14 03:29 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
6starprez Offline


Registered: 02/25/12
Posts: 8
Loc: North Carolina
I doubt your 2014 Kia Forte 2.0 GDI calls for a 5W30. I'm sure the required oil is 0W20 or 5W20 and using a 0W in place of 5W will not void your warranty.
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#3389884 - 06/05/14 03:38 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: 6starprez]
Jasper8146 Offline


Registered: 04/25/10
Posts: 157
Loc: Lenexa, Kansas
I just double checked the owner's manual and 5W-20 and 5W-30 are both recommended for all temperatures. Surprisingly, it even says 10W-30 is okay for temperatures of 0 fahrenheit and above.

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#3389889 - 06/05/14 03:43 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
4wheeldog Offline


Registered: 04/23/12
Posts: 117
Loc: East Mountains, NM
Originally Posted By: Jasper8146
I just double checked the owner's manual and 5W-20 and 5W-30 are both recommended for all temperatures. Surprisingly, it even says 10W-30 is okay for temperatures of 0 fahrenheit and above.


You will see a bigger difference in mileage (Although still very small) between 5/30 and 5/20 than you will between 5/20 and 0/20.

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#3389895 - 06/05/14 03:49 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
SLATRON Offline


Registered: 10/20/13
Posts: 223
Loc: upstate NY
Amsoil site says 5w20 or 5w30 at all temps but 5/20 is preferred, & 10w30 ok above 0*f
Using a 0 grade instead of 5 won't make much MPG gains, but I feel most useful in winter months for cold starts.


Edited by SLATRON (06/05/14 03:53 PM)

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#3389900 - 06/05/14 03:52 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
901Memphis Online   content


Registered: 08/14/10
Posts: 4875
Loc: Northern Kentucky
I would use a synthetic 5w20 during the warranty period.
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#3389911 - 06/05/14 03:58 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
tig1 Offline


Registered: 01/03/09
Posts: 9699
Loc: Illinois
Possibly.
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#3389926 - 06/05/14 04:07 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: Jasper8146
I just read the Motor oil 101 to 109 here on BITOG and if I understood correctly what he was saying, it seemed to me that he was saying that all motor oils were actually too thick at room temperature to give optimal lubrication and optimal mpg at initial start up but that 0W oils were thinner than others and thus minimized the problem.

That makes sense, good advice. Look at it this way, the "perfect" oil-of-the-future will not get much thicker when cold and not thin out when hot, same viscosity all the time. We can't do that with current technology, but we can get closer to that when we use a 0W-20.

Originally Posted By: Jasper8146
So, my question is for a 2014 Kia Forte 2.0 GDI which recommends 5W-20 or 5W-30, if I'm not doing any abusive driving or high speed driving in Arizona during the summer, would 0W-20 and 0W-30 be better choices if my goal is to achieve the highest fuel economy? Am seriously thinking about the Toyota 0W-20 as it seems to have gotten rave reviews here on BITOG and other places. On the other hand, I don't want to jeopardize the warranty either, especially if using the 0W-20 is not going to make a meaningful difference in mpg. What are people's thoughts here about this? This vehicle only has 2300 miles on it and am just about to do my first oil change. Thanks in advance for the input.


Like others have said, there is a small fuel economy advantage to using a 0W-20. Small. Anyway, we have had similar discussions about durability of engines using a 20 vs. 30 (or 40), and, to me, this sums it up: http://priuschat.com/attachments/fuel-efficient-motor-oil-technical-article-pdf.11772/ I don't think a 20 is a durability problem, and just looking at the Stribeck Curve convinces me the Shell tribologists are right, saying no problem.
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#3389957 - 06/05/14 04:33 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: FetchFar]
Shannow Offline


Registered: 12/12/02
Posts: 26073
Loc: a prison island
Originally Posted By: FetchFar
and just looking at the Stribeck Curve convinces me the Shell tribologists are right, saying no problem.


Can you explain how you look at the Streibeck curve, without knowing either the geometry or the applied load ?

Bottom axis is (operational viscosity x surface speed / applied load).

Unless you know those, you can't read the Streibeck curve.

Unless I'm missing something and there's another way.

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#3390020 - 06/05/14 05:52 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Shannow]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: Shannow
Bottom axis is (operational viscosity x surface speed / applied load.


Not "load", its actually pressure. Thats load per unit area, maybe thats where the missing geometry you mention comes from. Therefore, more surface area means a thicker oil film, all other things (visc, speed) being equal.
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'11 Chevy Camaro LS, 3.6L V6, Zeta chassis, 312 hp
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#3390026 - 06/05/14 06:04 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Shannow]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: Shannow
Can you explain how you look at the Streibeck curve, without knowing either the geometry or the applied load ?


I discussed this before on these forums in more detail, but, essentially, the bearing engineer knows the worst-case load force (max torque), at a low rpm (lugging), and knows what viscosity oil he wants to use, and then he determines the bearing surface area that will give minimum friction on the Stribeck Curve plus some margin to allow for normal viscosity drops with oil ageing (fuel dilution, VI degradation, etc.). A good choice would be a Stribeck Curve choice of 0.4 on the http://www.stle.org/resources/lubelearn/lubrication/ chart, near minimum friction, yet allows for less viscosity should it occur. .... Now notice the small difference between a 30 oil vs. a 20 oil, and notice that using the thinner oil really doesn't move you to the left on the Stribeck Curve much at all (notice log scale).
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'11 Chevy Camaro LS, 3.6L V6, Zeta chassis, 312 hp
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#3390079 - 06/05/14 07:31 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
Shannow Offline


Registered: 12/12/02
Posts: 26073
Loc: a prison island
I'm fairly familiar with the curve, and that the applied load is pressure...how do you know what the applied load (pressure) IS for the different geometries and families of engines ?

...and therefore where on the curve that you are when stating that 20s are right ?

You also need to get the right curve that includes the extensi0n off to the left for friction modified boundary conditions, because as per the paper you linked a few posts back, engines are increasingly operating way off to the left of the chart (which, yes, is logarithmic)

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