Can there be an oil that flows better than 0W?

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Now or in the future..................................? I hear a lot of 5W oils flow better than 0W oils at low temps. So everytime i look at a Group III "0W" (Mobil 1) vs a Group V synthetic (Redline, mail order) or Group IV (Royal Purple, API SL, off the shelf,) I ask myself how much im losing on the 0W. And yes, GC is a thick 30 that is still a 0W. So, is either ok? Or is synthetic vs. conventional, or even basestocks, an issue here with below-zero and or cold-weather flow and lubrication performance? Id be most confused as to whether to seek out a 0W-20 or 5W-20 for this 1991 Civic CRX Si im picking up. High mileage runs fine like most all CRXs... 3.75 Qts of oil lol thats 4 quarts smile Was going with Castrol Edge for that one. Tossed around the idea of putting RP 5W-230 in there to. At 4 quarts i can spend whatever i need to on a good oil and simple PureOne filter for it. Going with 20, not 30.
 
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As to the original question: Of course an oil can be made to flow 'better' than a 0 weight. The 0 # is arbitrary. I don't know what you are "losing" on the 0W. I don't know what that means, or the rest of the post.
 

JHZR2

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The selection of 0w, 5w, 10w is related generally to the ambient conditions when you are starting. The fact that an oil is group III or IV or V has nothing to do with it, what is the viscosity at the temperature of interest? If your minimum cold temp is much higher than the rated 0w temp, there is a chance that the oil may be thicker than another oil where your temp of interst is closer to the rated temperature. There is a lot to this. In TX it is somewhat irrelevant for much of the time, and I'd go for a 5w-20 to minimize viscosity spread.
 
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You're over thinking this. In your climate, if you want the lightest oil possible, that would be an oil with the highest VI and lowest HTHSV. What could be simplier? For your CRX, the only way to know for sure if you can run a light 20wt oil in the heat of a Texas summer is with a oil pressure gauge, otherwise you're just guessing. In the meantime, I'd stick with an OTC 5W-30 with a HTHSV of 3.0cP -3.1cP and a VI of at least 170. Oils that would fall into this range would be M1, PP, PU and Edge to name just four.
 
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Im not sure exactly what your asking. I dont believe pour point has been used since the days of 20W-20. 0W Pumping Test is at -40. 5W Pumping Test is at -35C. Either could pour better depending on temperate and viscosity index of the specific oil. If your asking specifically which will be better if you have to start your engine at -40 to the best of my knowledge no 5W will be the equal of any 0W. I guess its possible a specific 5W might pass the -40 pumping test by a larger margin than a specific 0W and yet remain 5W rated because it failed the cold cranking test for 0W.
 

45ACP

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OK so i would be advised to use Edge 5W-30 as i dont think Edge has an 0W-30, or an 0W-30 AFE from M1 before automatically finding an 0W-20 or 5W-20 (edge) for the car. And anything without an oil pressure gauge is just guessing. Thats what i wanted to know! smile
 
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Originally Posted By: JHZR2
In TX it is somewhat irrelevant for much of the time, and I'd go for a 5w-20 to minimize viscosity spread.
Don't agree. There is a benefit to having the lightest oil on start-up even in the summer. If you want to "minimize viscosity spread" that won't be accomplished that with a 5W-20 oil as that grade tends to have a very low viscosity index. To minimize "viscosity spread" you want the highest VI possible and that tends to be associated with 0W oils and definitely so with 20wt oils.
 
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Originally Posted By: 45ACP
OK so i would be advised to use Edge 5W-30 as i dont think Edge has an 0W-30, or an 0W-30 AFE from M1 before automatically finding an 0W-20 or 5W-20 (edge) for the car. And anything without an oil pressure gauge is just guessing. Thats what i wanted to know! smile
Yes, and to emphasize, the purpose of the OP gauge is to make sure you have adequate OP in your old Honda. I'm sure you can likely run a 20wt oil if the engine is in good shape, but again we don't know for sure. BTW, while I recommended Edge in the 5W-30 grade I do not recommend it in the 20wt grade; there are better choices.
 

JHZR2

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Originally Posted By: CATERHAM
Originally Posted By: JHZR2
In TX it is somewhat irrelevant for much of the time, and I'd go for a 5w-20 to minimize viscosity spread.
Don't agree. There is a benefit to having the lightest oil on start-up even in the summer. If you want to "minimize viscosity spread" that won't be accomplished that with a 5W-20 oil as that grade tends to have a very low viscosity index. To minimize "viscosity spread" you want the highest VI possible and that tends to be associated with 0W oils and definitely so with 20wt oils.
I concur with what you say, but my point is that as you transit along the viscosity/temperature curve, it is highly probable that a 5w is thinner than a 0w (maybe even a 10w is thinner than the 0w) for some range of ambient temperatures of interest. Sure, some people make "curves" but that isnt reality. They havent been proven with the rheometric data to verify the trend. So my point is that in Dallas, 30 or 40F may be his minimum temperature. A 5w may well be thinner at the startup temp than the 0w. Heck, in the summertime, a 20wt straight may be thinner than the 5w-20. If you look at the 40C viscosity of straight 40wt oils, you see that they can be "thinner" there than 5w-40 and 15w-40. Its all about what your temperature is.
 
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Originally Posted By: JHZR2
Originally Posted By: CATERHAM
Originally Posted By: JHZR2
So my point is that in Dallas, 30 or 40F may be his minimum temperature. A 5w may well be thinner at the startup temp than the 0w. Heck, in the summertime, a 20wt straight may be thinner than the 5w-20. If you look at the 40C viscosity of straight 40wt oils, you see that they can be "thinner" there than 5w-40 and 15w-40. Its all about what your temperature is.
The measure of how much an oil's viscosity changes with temperatures above freezing is the viscosity index. For the most part 0W oils have higher VIs than 5W oils and the greater the sprend of an SAE grade, generally the higher the VI. Having said that, if you want a better handle on the actual viscosity of any oil you must look past the SAE grade. The most accurate measure of viscosity at operating temp's is the HTHS viscosity. If you want the lowest possible viscosity on start-up down at least to the freezing point, first choose the lowest HTHSV that's acceptable for your application and then the oil with the highest VI for that HTHSV. It's that simply.
 

JHZR2

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Originally Posted By: CATERHAM
The measure of how much an oil's viscosity changes with temperatures above freezing is the viscosity index. For the most part 0W oils have higher VIs than 5W oils and the greater the sprend of an SAE grade, generally the higher the VI. Having said that, if you want a better handle on the actual viscosity of any oil you must look past the SAE grade. The most accurate measure of viscosity at operating temp's is the HTHS viscosity. If you want the lowest possible viscosity on start-up down at least to the freezing point, first choose the lowest HTHSV that's acceptable for your application and then the oil with the highest VI for that HTHSV. It's that simply.
Operating temperature is irrelevant here. We are talking about an intermediate temperature that is not the "rating temperature" for a 0w- or 5w- oil, e.g. -40C or -35C, nor is it the 40C or 100C temperature. The issue is flow at startup, not operation. It is inbetween, maybe below freezing, maybe not. And that is the point. Some oils will have a more substantial viscosity change with temperature. Some will havea more gradual change. The lower the spread, the more gradual the change need be, and thus some of the higher "w" numbers may actually be thinner at temperatures of interest to the OP, especially since he is in TX. I gave my example, a straight 40wt is thinner at 40C than a 5w-40 or 15w-40, regardless of what the VI or any other characteristic is. Look at the PDS. This may or MAY NOT be the case for the OP's oils, or the worst case temperature conditions of interest. But if he wants the optimum for some condition set, it needs to be looked into deeper. Otherwise there is just speculation, which is mostly what we have looking at PDSs and trying to correlate a -40C number to a +4-C and a +100C number.
 

45ACP

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Originally Posted By: Boss302fan
A 91 Honda would spec 5W or 10W-30 weight oil.....
Yup. Says 5W-30 on the cap. Debating whether or not to go Redline 0W-20 with her, which is a "Thick" 20-weight. For all 4 quarts this little 1.6 uses.
 
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Originally Posted By: JHZR2
Originally Posted By: CATERHAM
I gave my example, a straight 40wt is thinner at 40C than a 5w-40 or 15w-40, regardless of what the VI or any other characteristic is. Look at the PDS. This may or MAY NOT be the case for the OP's oils, or the worst case temperature conditions of interest. But if he wants the optimum for some condition set, it needs to be looked into deeper.
I don't know why you're referencing an obsolete straight mineral 40wt oil, but since you brought it up I pulled up the spec's of Castrol Classic XXL 40. KV40 155cSt, KV100 14.89, V1 95. A straight 40wt oil is thicker that a typical 15-40 dino (forget a 5W-40 as that is massively lighter) at all temp's below about 90C. At room temp' the staight 40wt is about 70% heavier and 250% heavier at 0C. The problem is the oil's low 95 VI. As I explained, the lightest oil on start-up at temp's down at least to freezing, is the oil with the highest VI and the lowest HTHSV.
 
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