is 0W-20 always better for mpg than 5W-20?

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Originally Posted By: FetchFar
And yes, any design engineer would place it around 0.4 (maybe upwards of 1). Put 8 cs in instead of 10 cs (again, 20 vs. 30), worst case moves the 0.4 to 0.3 ---> Not much movement on the Stribeck, obviously. The point.


Again, you are stating that you are GUESSING what a designer WOULD do...and using that to make your recommendation that running to the left is still hydrodynamic...you aren't even trying to use science, you are GUESSING what the designer's intent was, and GUESSINg that it will all turn out alright, all of the time.

Originally Posted By: FetchFar
Originally Posted By: Shannow
Except that means that they LOSE their designer installed safety margin,...

The discussion was, in going from a 30 to a 20 weight, and we see that only moves the Stribeck a small amount. Emphasis on SMALL amount. Very little margin lost.


Again, you biring up Streibeck, as 'though it adds validity to your argument, when you are GUESSING at where on said curve it would be...at least others have the honesty to say that the manufacturer's have a margin, and short of overheating/tracking, you won't use it up in "normal use", rather than brigning in a curve that they have no comprehensible idea of where the designers put it...as you say, you could be out bu a factor of 2.5 (0.4 to 1), which if your GUESS is wrong puts it on the wrong side of hydrodynamic

Originally Posted By: FetchFar
The ZN/P for the crank journal bearings SPECIFICALLY remain hydrodynamic for running conditions, a very important point to remember.


Do they ?

that's not what the paper I linked said, nor what Honda say in some of their 16 grade documentation.

You are ASSuming that bearing remain hydrodynamic...in design, I would always make sure that a bearing is hydrodynamic, but my stuff is supposed to run for 200,000 hours, not achieve "adequate" life in a semi disposable appliance,subject to regulators like CAFE


Originally Posted By: FetchFar
End of discussion for me.


Yep, that is always a convincing point


Originally Posted By: FetchFar
I'll just let the "Improved Fuel Efficiency by Lubricant Design : A Review by R.I. Taylor & R.C. Coy, Shell Research & Technology Centre, Thornton, United Kingdom paper take it from here. Address all questions to Shell from now on please. LOL...


I'll bold what I consider to be an important flaw in your guesswork house of cards.

Originally Posted By: FetchFar
"In our laboratory, it has been observed that in a modern gasoline engine, well designed automotive bearings can be lubricated with oils as thin as 2.3 mPa.s (and a 20 weight oil has 2.6 to 2.9 mPas) without any observable wear on either con-rod or main bearings.


I agree with them, however, they are talking about bearings that are designed for the lubricants and operating conditions. They are not saying that 2.3 will protect every engine that's ever been made, which is a common assertion on this site.

They are also not
* GUESSING on a designer's intent
* GUESSING where the designer put the bearing on the Streibeck Curve,
* calculating where the first guess would take them with a change in viscosity
* GUESSing that it will all therefore be OK; then
* making a recommendation on all engines, all designs, based on a card house of guesswork.

Even if the answer is correct (it doesn't fail), the train of thought to get to the conclusion is flawed, and illogical...

illogical UNLESS you KNOW where the bearing in question actually IS on the streibeck curve.

Otherwise "she'll be right" saves space on the message board.
 
Originally Posted By: Shannow

illogical UNLESS you KNOW where the bearing in question actually IS on the streibeck curve.


Just spell Stribeck correctly please. LMAO

Not only are the Shell tribologists correct, the entire discussion I clearly layed out explains why Ford for example has easily been able to specify 30-weight oils for their engines in Europe and 20-weight oils in the U.S. for about 10 years now, same engines.

You lose this argument based on the facts and analysis, both.
 
Originally Posted By: Clevy
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


Exactly.

Here's the key point:

An oil's xW rating describes its viscosity at a very specific, very cold temperature.
The xW rating says NOTHING about the oil's thickness at moderate temperatures.
Depending on where in Arizona the OP is located, this oil may never get colder than 65~70f.
Further, the visc. plot from -35f to 60f is not linear! As the oil is chilled, fractions of the oil will crystallize, causing the visc to rapidly increase at key temperatures. This gives you a stair-step visc/temp plot which is utterly and completely unsuited for calculating 70f visc.

If you want to estimate visc. at Az starting temps, you'd be better off using the oil's VI to extrapolate down from the stated 100C visc.
 
Usually car maker have have two goal,1 :best bang for $ (to achieve lowest maintenance cost )2 stay to about 10 psi per 1000 rpm(optimal flow/pressure for temperature regulation of oil
 
Also some part maker (allison come to mind)had to create their own rule(exemple:300 hour corrosion test on yellow metal)why?because oil maker tend to always do the minimum required if it isnt spelled in big letter,that is why big rig oil requirement were so thorowly spelled .and it will be even more stringent in 2018 .todays diesel run at 230 f (oil)this means the 212 test is pretty much irelevent for todays trucks.i m sure care will follow
 
mpg between 5w-20 and 0w-20 is 3/5 x 7/8 x 0 = 0 in this instance.

Are you trying to split hairs ?

Vehicle maintenance such condition of spark plugs and leads, tyre pressure, quality of fuel, air filter condition, traffic route selection, removal of unnecessary weight/parcels in the vehicle is far more important and has greater impact on mpg regardless whether the OEM specifies either a 5w-20 or 0w-20.
 
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Originally Posted By: CATERHAM
Jasper8146, as others have mentioned, your car is spec'd for the 5W-20 grade so in a warranty situation it is possible that you could be questioned as to why you're using a 0W-20.
Now if you're not concerned with that then yes you can use a 0W-20 and even the TGMO 0W-20 as a number of Hyundai/kia owners have with good UOA results. But be advised that TGMO is one of lightest 20 grade oils available so in your climate, since your car is not equipped with oil gauges to monitor things I'd suggest substituting a 1/2-1 quart of M1 0W-40 to give your a somewhat heavier 0W-20 oil. It will still be lighter on start-up than all 5W-20s and even most aftermarket 0W-20s, but it will retain a higher high temp' viscosity.


Why not promote the OP to find a ?w-20 oil with the appropriate builder approval. The OEM would quiver how freely it it is touted mix this with that to come up with what ?

Surely with the huge range oil of brands for selection in that grade you have in the USA, compared to OZ, there must be one on the shelf you can add with confidence in an unadulterated form straight out of the container.

Unbelievable from my view point in OZ.
 
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I use 0w20 in my '08 Hyundai Accent. 104k miles and runs like a champ. Uses about a 1/2 qt in a 7500 mile OCI. I think the only reason you don't see 0wx oils in the manual is they would have to be synthetic.
 
Could any explain to me why the majority of car maker say to use
5wxx ?how come almost all car maker never say 0wxx .what is wron with a 0wxx oil?is it an issue in the dino version?
 
Originally Posted By: yvon_la
Could any explain to me why the majority of car maker say to use
5wxx ?how come almost all car maker never say 0wxx .what is wron with a 0wxx oil?is it an issue in the dino version?


Because it requires a synthetic and is more expensive. OEM's that generally aren't German usually don't make it a policy to spec (expensive) synthetic oil.
 
Originally Posted By: virginoil
Originally Posted By: CATERHAM
Jasper8146, as others have mentioned, your car is spec'd for the 5W-20 grade so in a warranty situation it is possible that you could be questioned as to why you're using a 0W-20.
Now if you're not concerned with that then yes you can use a 0W-20 and even the TGMO 0W-20 as a number of Hyundai/kia owners have with good UOA results. But be advised that TGMO is one of lightest 20 grade oils available so in your climate, since your car is not equipped with oil gauges to monitor things I'd suggest substituting a 1/2-1 quart of M1 0W-40 to give your a somewhat heavier 0W-20 oil. It will still be lighter on start-up than all 5W-20s and even most aftermarket 0W-20s, but it will retain a higher high temp' viscosity.


Why not promote the OP to find a ?w-20 oil with the appropriate builder approval. The OEM would quiver how freely it it is touted mix this with that to come up with what ?

Surely with the huge range oil of brands for selection in that grade you have in the USA, compared to OZ, there must be one on the shelf you can add with confidence in an unadulterated form straight out of the container.

Unbelievable from my view point in OZ.

Yes virtually every oil brand offers something in a 5W-20 and now the 0W-20 grade in NA but as I mentioned Hyundai/Kia don't spec' the 0W-20 grade just 5W-20.
The OP could use M1 0W-20 which Mobil states will not void any companies warranty when used when 5W-20 is specified but that's about it.
The OP inquired about using TGMO 0W-20 and is the reason for my response. If he was interested in something a bit heavier without blending, SynGard 0W-20 (220 VI, HTHSV 2.7cP) would be an option but it is not as readily available.
 
Caterham the vehicle in question is a 2014 under warranty it puzzles me why in this instance you promote a mix this and that to get who knows what.

If the OP is off the mark I would expect an experienced BITOGer to inform the OP to follow OEM directions.

This is my view, like you have yours, and the longer I spend on this forum I am seeing the OEMs perspective clearer and clearer.
 
I don't want to generalize with engines and climates I'm not familiar with.

However, here in hot and humid South Florida, thinner oils result in higher UOA wear metals, in my "fleet". Others have different results. I'm hard on things, it seems.
 
Whether under warranty or not is irrelevant.
For the most MPG, use any full synthetic 0w20.
You probably wont see the mpg difference when compared to a full synth 5w20.
When the transmission is due for service, use a full synth fluid there too.
 
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