Does 5w30 really offer better engine life?

Patman

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For a few years now the automakers have been pushing 5w30 down our throats, and part of their selling point is that they say the 5w30 oil will flow faster and offer better cold start protection than good old 10w30. I believe this to be true in the cold wintertime, but is it honestly going to be any different in the warmer months? Have you guys seen any oil analysis data which proves that 5w30 provides better engine wear on the new cars compared to 10w30? I just feel that the 5w30 was brought out as a fuel economy oil only, much like 5w20 now too. *please take note that this topic was originally started in 2002, someone bumped it to the top today*
 
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Agree...N.A. cafe standards only...I always found it interesting that with all of the improved pourablility of synthetics...why they needed a "0" grade. Who's out there that needs startability in -65F??? when a synth. 5-x will start in -55F?
 

Patman

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Someone correct me if I'm wrong, but I seem to recall that Amsoil 5w30 used to have a pour point of -78F! With pour points like that, who needs 0w30 for sure! At that time I think their 10w30 also had a similar low pour point.
 
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Posted by Patman: For most new cars, it is my belief that 10w30 is the best viscosity for all weather other than the cold winter time. I still think 5w30 was simply adopted because of fuel economy, and the added VI improvers in it are a detriment to it's overall performance. Glade to see Patman has changed his thoughts on this one.
 
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There was a time when that was probably true. Today's oils are light years improved over the "good old days".
 
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A conventional 5W oil at temperatures of -25 C or lower unaided for starting really do not protect too well. 0W is basically a category for insane cold performance, -40 type arctic oils. They are made for a purpose but they fit inside the curve for viscosity until they are nearly at operating temperature which does help economy.
 
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Whether it is 0W/5W/10W, the W number is based on pumpability. The 30 is determined by the 100C cSt viscosity. Mobil 1 10W-30 has a 100C cSt viscosity of 10. Mobil 1 0W-30 has a 100C cSt viscosity of 11, and Mobil 1 5W-30 has a 100C cSt viscosity of 11.3 Either the 0W or 5W give a little better high temperature engine protection and stay in grade at higher temperatures better than the 10W. The 0W-30 has a 40C cSt viscosity of 63.1 and the 10W-30 is only 62!. I am using a 5W-30 with a 100C cSt viscosity of 12.4. A 0W-30 could be a higher viscosity/ thicker oil than a 10W-30 oil, both at 40C and 100C, yet have much better cold pumpability. The ending 100C cSt viscosity for a 30 grade is 12.5 and that is also the beginning cSt for a 40 grade. In theory, a 0W-30 grade COULD BEHAVE as a 0W-40!!, 5-30/5-40, 10-30/10-40. I was super confused until someone with lots of patience and a good temperament explained that the numbers such as 5W-30, or 15W-40 were grade numbers and did not necessarily indicate the viscosity/weight, only the grade. The issue is the VII and with modern synthetics not as many/much are needed and they are greatly improved. I believe it would take a 5W-30 with a 100C cSt of 11.3(or 12.4) more miles to shear out of grade that it would take the 10W-30 with a 100C cSt of 10 to 10.5.
 
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 Originally Posted By: TallPaul
Well, I'm still sticking with 10w30.
Me, I'm sticking with what comes cheap, what's rated SM/GF4, and of course, my 5K OCI. What more could a 4-banger roller-skate Hyundai ask for?
 
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 Originally Posted By: toocrazy2yoo
 Originally Posted By: TallPaul
Well, I'm still sticking with 10w30.
Me, I'm sticking with what comes cheap, what's rated SM/GF4, and of course, my 5K OCI. What more could a 4-banger roller-skate Hyundai ask for?
Ooo, a 4-banger! Perfect opportunity for the double redline: Redline Oil and Redline it through all gears! Extend the OCI and it will be almost as cheap, and with added protection.
 
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The first place that I would look in choosing a motor oil would be the owner's manual and other information from the manufacturer......like Techinical Service Bulletins (TSB's). If the manual calls for 10W-30.....then that is what I would use....unless I found a TSB from the manufacterer that says otherwise.
 
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 Originally Posted By: FrankN4
Whether it is 0W/5W/10W, the W number is based on pumpability. The 30 is determined by the 100C cSt viscosity. Mobil 1 10W-30 has a 100C cSt viscosity of 10. Mobil 1 0W-30 has a 100C cSt viscosity of 11, and Mobil 1 5W-30 has a 100C cSt viscosity of 11.3 Either the 0W or 5W give a little better high temperature engine protection and stay in grade at higher temperatures better than the 10W. The 0W-30 has a 40C cSt viscosity of 63.1 and the 10W-30 is only 62!. I am using a 5W-30 with a 100C cSt viscosity of 12.4. A 0W-30 could be a higher viscosity/ thicker oil than a 10W-30 oil, both at 40C and 100C, yet have much better cold pumpability. The ending 100C cSt viscosity for a 30 grade is 12.5 and that is also the beginning cSt for a 40 grade. In theory, a 0W-30 grade COULD BEHAVE as a 0W-40!!, 5-30/5-40, 10-30/10-40. I was super confused until someone with lots of patience and a good temperament explained that the numbers such as 5W-30, or 15W-40 were grade numbers and did not necessarily indicate the viscosity/weight, only the grade. The issue is the VII and with modern synthetics not as many/much are needed and they are greatly improved. I believe it would take a 5W-30 with a 100C cSt of 11.3(or 12.4) more miles to shear out of grade that it would take the 10W-30 with a 100C cSt of 10 to 10.5.
What you say here makes since, but it appears most 5W-30 oils we see here shear down to almost a 20W where the 10W-30's do not.
 

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For anyone interested in the (poor) shear stability of M1 5W-30, there are plenty of UOAs showing how low its viscosity drops. It's often to less than 10 cst. That is from 11.3 cst to "9 something" cst. Some of that may be from fuel dilution as occurs with any oil but that is a large change for a name-brand 5W-30 synthetic. M1 10W-30 has more stable viscosity and what counts on the high temperature end is the used oil's HTHS viscosity which certainly will exceed M1 5W-30's value since it starts off that way and the gap only grows as the oil is used longer.
 
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I've always felt that, all else equal, a thicker base oil is a good idea. 10w30 will have thicker base oil than same brand's 5w30. Thicker base oil is a large component of HTHS. Modern energy conserving oils have lower HTHS because the VIIs collapse through the bearings to reduce friction for better CAFE mpg numbers. It's all about saving dollars. Dollars first, then make engine wear work out. I prefer to address engine wear first and then worry about the dollars.
 
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In most cases (YMMV) the oil that aids in processing the least amount of fuel through the engine will produce the longest engine life (naturally, terms and conditions apply).
 
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If a thinner oil provides better mileage isn't it reducing friction which would be causing engine wear? Frank D
 

PT1

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 Originally Posted By: Patman
For a few years now the automakers have been pushing 5w30 down our throats, and part of their selling point is that they say the 5w30 oil will flow faster and offer better cold start protection than good old 10w30. I believe this to be true in the cold wintertime, but is it honestly going to be any different in the warmer months? Have you guys seen any oil analysis data which proves that 5w30 provides better engine wear on the new cars compared to 10w30? I just feel that the 5w30 was brought out as a fuel economy oil only, much like 5w20 now too.
According to my GM & Ford engine design friends 10w30 is better. Ok start the flame thrower.... However the MPG difference in my Yukon 6.0L is about 2.3 MPG better with the 5w30 so the 10w30 really seems to hog the fuel. This is with both M-1 & PP that I have tried. Now a blend of 50/50 5w30 & 10w30 PP gives me a 7.5w30 and the engine seems to like it. But I lose 1 mpg. I'm getting just over 16 mpg with the pp 5w30 in the city and about 19mpg hwy ( 65mph or less). so it 5w30 for me.
 
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