0w or 5w-20 for gas mileage?

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so whats the whole deal about 0wts? I mean, isn't the purpose of real thin oil, to help cold start up? I know theres amongst other reasons, but in my case, I will be barely hitting operating temperatues with my oil..becuz of my driving style...SOOO, wouldn't 0w-20 or 5w-20 help me with engine life + improve gas mileage?

I know every car is different...and nothing is perfect in this world...and the only way to tell is to get an UOA from blackstones...but I just wanted to know the general consensus from u guys
 
Originally posted by Gary Allan:
quote:
But using any higher viscosity than is necessary just has no legit presence in any rational thought process.
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Click to expand...
But using any [lower] viscosity than is necessary has no legit presense in [my] rational thought process.
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The deal is that if it is extremely cold outside (below 0º F) that the oil will flow quicker at start up. It is probably nice and warm year round in CA. It isn't an issue. Stick with the recommended 5W-30 and worry about more important things in life. You will not notice a major improvement in fuel economy using 5W-20 and you will be very well protected with 5W-30. Do you sit in traffic jams a lot there?
 
Man In Black:

As to how 5W20 can hold up, go into the UOA forum. find the first ten Motorcraft 5W20 UOA you see.
That's how. It defies common sense, but that oil can take a beating.
Also, speeding isn't hard on your engine or oil. If you drive fast enough to really tax your engine, you're either driving a vintage VW Bug or you'll lose your license within the week.
As far as towing goes, you're right... that does heat things up. Believe it or not, high outside temps won't make a difference if you're not also loading the engine down with work to do; a modern cooling system can do a LOT of work in that regard.
 
steven88. A "0w" oil is only possible with a synthetic. Your probably not going to be able to use it long enough to make it pay over a 5w-20 semi-synth that's available for about half the cost. You may surely be able to get one year out of a synth OCI ...but you will probably get at least 6 months out of a semi-synth. The UOA will tell the real story.

The evolution to thinner oils is to reduce the energy required to pump them through the engine. This they've been doing since the late 70's. Most cars ...the vast majority, are in warm up their entire lives. Full warm up (the nomenclature used by our engineers, researchers, and oil companies is "startup") takes a long time. When you hear "90% of engine wear occurs during startup" ..what they're not telling you is that 90% of the time you drive you're in what they call "startup". Most of any engine's wear is unavoidable. So ..you make them (the oils) leave less deposits ..consume less power to pump ..enable them to last longer in service.

One of the byproducts of the creation of our 5w-30 oils (the stuff many have been using for decades) is that we've found that most engines can work just fine on 20 weight oils. This is due to the fact that most 5w-30 dino oils shear to a 20 weight routinely. Most have been using 20 weight oils for 25-30 years and didn't even know it.

Now they've come up with 20 weight oils that remain 20 weight oils ..so no reason for starting out heavier. They can "cut to the chase".

Again, use it. If you gain no benefit in fuel economy ..there's really no reason to use the, typically more expensive, lighter oils. If you do ..then do your UOA. It's the same UOA ..done at exactly the same time. You just determine what you're going to put in it after you drain the 5w-20 based on apparent gains. If you do not ...don't bother with the UOA unless you're really curious ...since that's not likely to be the oil that you'll put back in. Wait until the next OCI is ready to dump.
dunno.gif
 
quote:
Originally posted by Clyde65:
Originally posted by Gary Allan:
quote:
But using any higher viscosity than is necessary just has no legit presence in any rational thought process.
Click to expand...
Click to expand...
But using any [lower] viscosity than is necessary has no legit presense in [my] rational thought process.
smile.gif

Click to expand...
Well, I agree. It's an equally 'valid' statement. I would suggest that you find out what is the lightest weight that serves your needs instead of assuming that you need heavier.

That's why some perform UOA. They want to know.

Keep in mind that if you're talking domestic iron ..they don't spec (very few exceptions) a synth oil ...so the spec's assume our common dino oils. They take all this into account in spec'ing the oil weight.
 
Viscosity changes logarithmically with temperature. If you plot two points for cSt/temp, on semi-log paper (or in Excel), you can draw a straight line through the points and extrapolate any viscosity/temp. If one does this for M1 5w-20 and 5w-30 it can be seen that there is a viscosity offset difference between the two oils, but they have the same slope. M1 10w-30, for instance has a different slope.

It’s much easier to see the differences in the viscosity/temperature relationship for different oils when plotted on a semi-log axis.
 
Sure. Care to take the time to put it together??
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But I think I disagree ..at least with the way you're describing it (or how I'm integrating it). These two figures are converging. By what I'm reading in your assertion the slopes are parallel ...and there would be a uniform 2.5CST spread at any given temp. Since these two oils obviously diverge as they get cooler ..they can't have the same slope. We can see, in the 150C example, that there is .9CST difference between them.

[ July 17, 2006, 03:05 PM: Message edited by: Gary Allan ]
 
When the axis that viscosity is plotted on is logarithmic then even when the lines are parallel the difference is viscosity is not constant. If the viscosity/temp relationship is plotted on linear x-y axis then you get two curves that diverge at low temperatures and tend to converge at high temps, asymptotically approaching 0.0 cSt.

I did a plot of the three M1 oils using Excel last week. An "eyeball" analysis indicated that 5w-20 and 5w30 had the same slope.

(Some resarch revealed the logarithmic relationship of viscosity vs. temp.)

quote:
Originally posted by Gary Allan:
Sure. Care to take the time to put it together??
smile.gif


By what I'm reading in your assertion the slopes are parallel ...and there would be a uniform 2.5CST spread at any given temp.
Click to expand...
 
Okay ..sure. Now do a screen cap and put it up on a hosting site and link to it. (some SAE pro's have already done this somewhere ..but..)

....and ....

....(cue theme music) shw that as oil of different viscosities heat ..they become more alike....(now cue suspense music).....
 
Gary - Where did you get the viscosity/temp numbers from. From the Mobil on line data sheets I got:

40ºC/104ºF 100ºC/212ºF
5w-20 48.3 8.8
5w-30 64.8 11.3

The slopes of your numbers, plotted out, are different than the slope of the Mobile site numbers.

If you PM me with your email addy, I'll send you the spreadsheet.
 
Those are the numbers from the XOM website ..assuming I copied them correctly. Let's check.

I used those same numbers in this calculator and merely adjusted the temperture in the "new temp" field:

visc calulator

What you're saying is that your calculations produced a different slope

Mobil 1 5w-20

Typical Properties

Mobil 1 5W-20
SAE Grade 5W-20
Viscosity, ASTM D 445
cSt @ 40º C 48.3
cSt @ 100º C 8.8
Viscosity Index, ASTM D 2270 163
Sulfated Ash, wt%, ASTM D 874 1.0
HTHS Viscosity, mPa·s @ 150ºC ASTM D 4683 2.62
Pour Point, ºC, ASTM D 97 -47
Flash Point, ºC, ASTM D 92 228
Density @15º C kg/l, ASTM D 4052 0.80

Mobil 1 5w-30

Typical Properties

Mobil 1 5W-30
SAE Grade 5W-30
Viscosity, ASTM D 445
cSt @ 40º C 64.8
cSt @ 100º C 11.3
Viscosity Index, ASTM D 2270 169
Sulfated Ash, wt%, ASTM D 874 1.0
HTHS Viscosity, mPa·s @ 150ºC ASTM D 4683 3.09
Pour Point, ºC, ASTM D 97 -54
Flash Point, ºC, ASTM D 92 230
Density @15º C kg/l, ASTM D 4052 0.80

Those are the numbers I used
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[email protected]
 
Hey, pal ...you know I aim to entertain.
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b_rubenstein's cipherin' ability surely blows my abilities out of the water. Kinda like the UAE advanced F16's versus a WWI biplane ..but ..I don't think I offered it for the "truth" of the calculations in terms of absolute accuracy but merely to example how the "big differences" become smaller as you go hotter. Sure the contour is relatively the same ..but that "margin" of difference ...becomes ...marginal
smile.gif
 
In some cases ..marketing ..when you're talking synthetics. You can only get a 0w anything in a synthetic.

I think this is the first time I've ever heard a synth spec'd in a 20 weight. You're going to have a hard time finding off the shelf oil everywhere. I'd hate to see what the dealer will be charging for it.
 
quote:
Originally posted by Man In Black:
Gary I am not so sure. Using Mobil 1 as an example, 5W-20 is 8.8 cSt @ 100º C while 5W-30 is 11.3 cSt @ 100º C. That is a pretty big difference.
Click to expand...
@ 110C/230F

M1 5w-20
7.2
M1 5w-30 2CST
9.2

115C/239F
M1 5w-20
6.6
M1 5w-30 1.8CST
8.4

120C/248F

5w-20
6.1
5w-30 1.6CST
7.7

125C/257F
5w-20
5.6
5w-30 1.4CST
7.0

130C/266F

5w20
5.1
5w30 1.3CST
6.4

135C/

5w20
4.8
5w30 1.1CST
5.9


150C/302F
5w-20
3.8
5w30
4.7 .9CST

As you can see ..as they get hotter ..they look more alike.
 
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