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#1405439 - 03/16/09 09:35 PM 5w30 vs 10w30
05Blazer Offline


Registered: 12/04/08
Posts: 341
Loc: Illinois
I have switched my young 4.3L Blazer that sees fleet use to Maxlife Blend and have been very happy with the quietness of the engine and slowing of the cooler line leaks. I have always used 5w30 as per the owners manual & I am about to do an oil change for the summer and am wondering if I will see any benefit by switching to 10w30. After looking at the product specs on Valvoline's website they seem to have near matching numbers in every category except the 5W30 has a higher Viscosity Index rating of 163 vs. 10W30 146. This leads me to believe that the 5W30 might actually even be better period. Your thoughts?

thanks
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#1405458 - 03/16/09 09:52 PM Re: 5w30 vs 10w30 [Re: 05Blazer]
wannafbody Offline


Registered: 01/02/08
Posts: 894
Loc: PA
Theoretically the 5w should be better than a 10w at startup.
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#1405508 - 03/16/09 10:46 PM Re: 5w30 vs 10w30 [Re: wannafbody]
FrankN4 Offline


Registered: 04/18/08
Posts: 1093
Loc: Kentucky
You can only compare the VI of the same grade, XW-X to XW-X. You could not compare the VI of a 5W-30 to a 10W-30.

Check out this thread:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1399421&fpart=1
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#1405515 - 03/16/09 10:56 PM Re: 5w30 vs 10w30 [Re: wannafbody]
TallPaul Offline


Registered: 10/22/03
Posts: 12912
Loc: By Detroit
Viscosity index is meaningless unless you know the base oil and amount of viscosity index improver (VII) in the oil. An oil could have a very high VII and low grade base oil if enough VII is added, but would not necessarily be better than say a straight 30 which has no VII and a much lower viscosity index.

All else equal, there would be less VII in the 10w30, but many times all else is not equal. Two oils of the same brand may have some measure of better quality base oil in the 5w30 to make up for the wider spread, that is, so much Group III could be added to the 5w30 so the VII would not have to be boosted as much.

But I would run the 10w30 in summer since you don't need extreme cold starting properties.

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#1405531 - 03/16/09 11:14 PM Re: 5w30 vs 10w30 [Re: TallPaul]
Peter_Pan Offline


Registered: 07/07/08
Posts: 175
Loc: CA
One thing I've noticed consistantly when reading the data sheets for oils is that 10W-30 has a lower NOACK and higher density compared to 5W-30 which is expected more or less due to the differing amounts of VII added and his translates in to a more stable oil IMO. All said and done though, the difference is very small and you may not even feel a difference at all.

I agree with Paul, 10W-30 is a very good choice whenever temperatures are above 20-30 F.
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#1405680 - 03/17/09 07:36 AM Re: 5w30 vs 10w30 [Re: Peter_Pan]
Nickdfresh Offline


Registered: 03/15/06
Posts: 3300
Loc: Buffalo, NY
Both 5W-30 and 10W-30 MaxLife have a -42F pour point, so I doubt you'll notice much difference even in cold weather at start-up...

I would use the 10W-30 if doing a lot of highway driving since it will not sheer as much. Although, the 5W-30 ML is pretty "thick" at temperature so sheering is probably irrelevant...

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#1405693 - 03/17/09 07:55 AM Re: 5w30 vs 10w30 [Re: Nickdfresh]
TallPaul Offline


Registered: 10/22/03
Posts: 12912
Loc: By Detroit
Yes Peter Pan, NOACK is an excellent parameter to compare oils on.

I should clarify, viscosity index (VI) is largely based on the inherent VI of the base oil and the amount (and type) of viscosity index improver added (VII). So you never know how much of the VI is due to the quality of the base oil vs loads of VII being added. That's why I totally ignore VI as a parameter for evaluating/comparing oils.

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#1405694 - 03/17/09 07:58 AM Re: 5w30 vs 10w30 [Re: TallPaul]
addyguy Offline


Registered: 09/08/05
Posts: 13426
Loc: Canada
I'd run the 10W-30 during the summer. A touch thicker at lower temps, and may burn/leak a bit less.
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2003 Mazda Tribute LX V-6, 169k miles.
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