Viscosity and horsepower, a question for experts?

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799
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Washington, DC
My engine's (2000 mazda 626 2.5L V6) operating temperatre is around 100C. Looking at the data sheets from mobil1 I wonder how much horepower(given that my engine produces 170HP at 6000RPM) will I lose or gain by using M1 5W-40(0W-40) or M1 0W-20(currently in the car) this summer? Their respecive viscosities for 100C are: M1 5W-40 cSt @ 100ºC 14.8 M1 0W-40 cSt @ 100ºC 14.3 M1 0W-20 cSt @ 100ºC 8.4 How does higher viscosity rob engine of power? Does it show only at higher RPM or troughout the power band? I have done 3UOA so far you can see results here: http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=001291#000000 Thanks for your opinions! zoomzoom
 
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8,937
Location
SC
There is a reason why NASCAR engines run 0w20 and 0w30 oils. Same reason the specially blended oils for top fuel dragsters are straight 0w or lower. All things being equal, thinner oil will yield more HP. The trick is getting a thin oil that also gives acceptable levels of protection. For street use, this has pretty much been accomplished with the new 5w20 and 0w20 oils. For top fuel dragsters, all they are interested in is keeping the engine together for 1/4 mile.
 
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2,480
This is a complex question as thinner oils will yield less fluid resistance however, a thicker oil may seal the piston chamber better providing better compression. Furthermore, thinner oils tend to break down faster with resultant deposits which will rob HP.
 
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625
Location
Silver Spring, MD (USA)
Furthermore, thinner oils tend to break down faster with resultant deposits which will rob HP. The viscosity of the 0w-20 Mobil1 and its TBN is very stable at extended OCI's...that seems to disprove your statement. [ March 29, 2004, 03:32 PM: Message edited by: crossbow ]
 

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799
Location
Washington, DC
From what I understand thicker oil will give me more torque on lower end and will rob HP on uper end. Now I wonder how much difference would it be between 40wt and 20wt? 1-2% or 5%??
 
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22,188
Location
Colorado Springs
quote:
Originally posted by zoomzoom: From what I understand thicker oil will give me more torque on lower end and will rob HP on uper end. Now I wonder how much difference would it be between 40wt and 20wt? 1-2% or 5%??
If you took your car to a dragstrip and ran 5w-40 compared to 0w-20 on consecutive runs, I doubt you'd see much if any difference. A tenth or under at most, which is in the margin of error for things like wind speed/direction changing, atmoshperic changes etc. On a chassis dyno, you'd probably see an improvemnt of 5 horspower at most; I've seen magazine articles concuding this, BUT, they changed oil that already had a couple thousand miles on it. back to back with 5w-40 compared to 0w-20 would be 1-2 horsepower at most on a small V-6. For profesional competetive racing like Nascar, that would be over 10 hp for an 9,000 rpm small block V-8, and the fuel savings also means possibly 1 less green flag pit stop, which is the difference between 1st place, and getting lapped while in the pits getting fuel.
 
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897
Location
owatonna, mn
You're going to see a better gain by using any synthetic of a light weight compared to a conventional oil of a similar weight. This is because of the reduction of friction. Reduce friction by 50% and you're going to gain 5.8% power. You should be able to reduce friction about 20%. Use whichever Mobil1 you want and you'll be happy.
 
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555
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south texas border
Good link, but I wonder How applicable this is to my everyday driving. I currently run Torco Sr1 5w20. If it experiences an 18 % vis loss with the beginning vis being 7.3 @ 100, I think my little honda would be in serious trouble. Its early (only about 1500 miles on the oil). This makes me nervous enough to drop it early and UOA it. Of course euro 20w50 and US 5w20 may be a bit different. Time for a new car I guess [crushedcar]
 
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39,805
Location
Pottstown, PA
My understanding is that the hp savings aren't from the oil itself ..but the power robbed to pump it. Lighter oil ..less hp used to pump it. That's the rhetoric that I heard ...and it was the chief explanation for the evolution of the 5w-x and 0w-x oils. That is, it had little to do with the actual lubrication qualities of the oil at all ..just the power required to pump it. NASCAR engine builders btw have adopted a high volume/low pressure school of thought in their lubrication systems. It's used as much as a coolant as a lubricant.
 

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799
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Washington, DC
What is really interesting is that M1 0W-40 produced more power then GC 0W-30? That contradicts that statement that lower viscosity produces more power in a given engine? Why would this be the case?
 
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1,130
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California
Is the Castrol SLX 0W-30 in this article the same oil as "German Castrol" 0W-30 sold in the US? It was the best oil in their test for wear, third best on horsepower and turned in the lowest oil temperatures by far. All in all this seems to indicate a very well balanced high performance motor oil. John
 
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1,357
Location
California, USA
quote:
Originally posted by darkdan: You're going to see a better gain by using any synthetic of a light weight compared to a conventional oil of a similar weight. This is because of the reduction of friction. Reduce friction by 50% and you're going to gain 5.8% power. You should be able to reduce friction about 20%. Use whichever Mobil1 you want and you'll be happy.
Exactly where is this 20 percent friction reduction documented? Remember, you said compared to a similar weight of conventional and any synthetic.
 
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2,480
Guys, does this study rate the SLX 0-30 at the bottom of the pack with respect to the "Wear Metal Test"??? "The Wear Metal Test indicates the size and number of wear particle for each oil. The higher the rating the greater the number and size of wear particle" The SLX rated #11 (bottom) at 20-25 microns of "average particle size" at 15-100 microns overall. What does this mean with respect to protection????
 
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47
Location
Cleveland, Texas
quote:
Originally posted by jthorner: Is the Castrol SLX 0W-30 in this article the same oil as "German Castrol" 0W-30 sold in the US? It was the best oil in their test for wear, third best on horsepower and turned in the lowest oil temperatures by far. All in all this seems to indicate a very well balanced high performance motor oil. John
Actually, it looks like they meant to say that the higher (or larger) the rating number (numerically), the higher the wear, as GC's particles sizes were the largest, meaning it had the highest wear.
 
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764
Location
Fairfield County, CT
Is this even a valid test? They took samples out of used oil filters which were cut open! Seems highly inaccurate to me. I doubt you could get consistently repeatable results with such a method. Based on their method, you'd have to conclude (erroneously) that Auto-Rx causes lots of wear. Lots of huge particles in the oil filter when you use that... [Roll Eyes]
 

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799
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Washington, DC
well I'm not so much interested in ther wear results since I think the testing they used is not really good way to show wear... what makes me wonder is how this engine with 40wt oil is producing more power then with 30wt oil?
 
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