OK to use 10W30 when 5W30 recomended?

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I'm about to change the oil in my girlfriends 1999 Cougar 2.5 V6, the manual recomends 5W30, i would rather 10W30 for the summer here in Louisiana. Will this hurt the engine in anyway? Any info appreciated.
 

MolaKule

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In most manuals it says 5W30 preferred, but it might also say ok to use 10W30 or 10W40 for temps over 0 F. I am using 10W30 in my Nissan, as my user's manual allows it. I prefere that SAE grade because of the lower level of VII additive and the thicker lubricating films. 10W30, in my view, is a good compromise between sufficient lubrication protection and economy.
 

Patman

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IMO 5w30 was only created to satisfy CAFE. It's a fuel economy oil. 10w30 is more stable, and is better for long term engine protection, since it does not thin out as easily, and like MoleKule said, has less VII, so it should help keep the engine cleaner inside also.
 
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If you are using Mobil 1 products, the 0W-30, 5W-30 and 10W-30 are essentially the same.. Basically 30 weight base stock that just happens to pour at 60 below zero.. One might say the only difference between the 3 Mobil 1 oils is the label that is on the bottle....
 

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I have noticed a trend with Mobil 1 though, the 0w30 and 5w30 end up thinning out much quicker than the 10w30. You can see this on the Maxima.org oil analysis spreadsheet. It's probably more pronounced in cars that are driven hard.
 

wtd

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On two of my analysis's of Mobil 1 5W-30, I found the opposite to be true. It thickend up instead of thinning out. Wayne
 
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In the many oil analysis results I review each day, I do not see any "thinning out" of any of the Mobil 1's except in cases where the viscosities have been reduced by fuel dilution, A/F, etc.. In applications from cabs to tow trucks to NASCAR race cars to Honda's used by soccer mom's for shopping (the most severe test!).. Very, very shear stable.. Same with 0W-40..
 
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quote:
Originally posted by wtd: On two of my analysis's of Mobil 1 5W-30, I found the opposite to be true. It thickend up instead of thinning out. Wayne
Me too. My most recent analysis of Mobil 1 5W30 showed slight thickening.
 

Jay

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quote:
Originally posted by GeorgeCLS: If you are using Mobil 1 products, the 0W-30, 5W-30 and 10W-30 are essentially the same.. Basically 30 weight base stock that just happens to pour at 60 below zero.. One might say the only difference between the 3 Mobil 1 oils is the label that is on the bottle....
I wonder why Mobil 1's website says 0w-30 gives the best fuel economy of their 30 weight oils?
 
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quote:
Originally posted by GeorgeCLS: If you are using Mobil 1 products, the 0W-30, 5W-30 and 10W-30 are essentially the same.. Basically 30 weight base stock that just happens to pour at 60 below zero.. One might say the only difference between the 3 Mobil 1 oils is the label that is on the bottle....
Come on now. [Roll Eyes] Are we supposed to believe that? How do you suppose that the HTHS and NOACK are different, even according to Mobil. And that the TGA scans vary wildly between them. Also how does 5w30 and 0w30 attain higher mpg? Could it be that they shear down more? What do think of these: (thinned out) http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000065 http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000015 (mine, guess I already know what you think) http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000011 (Bob what happened to this one...it's hidden, only found it by search) And on Maxima.org spreadsheet, there is over 5 M1, 5w30 that have thinned out. But 10w30's on there have not... And about the two here that have thickened. I think that certain engines are more prone to shearing oils. Most likely high revving OHC engines, but that's just a guess right now. Because one was a turbo, i.e. it will burn off lighter molecules faster=thickening. The other is low revving OHV engine....
 
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I agree 100% with George on this issue .... I consider the Amsoil 0w-30/5w-30/10w-30 synthetics to be interchangable. The high temp properties of the Amsoil 5w-30 and 10w-30 are so close that the main reason I see for offering both is simply customer demand (I suspect this is also the reason why mobil markets all three SAE grades). I basically switched all my Amsoil 10w-30 customers over their Series 2000, 0w-30, as it does provide a fuel savings benefit. The 0w-30 and 5w-30 grades primarily achieve better fuel efficiency because they flow more easily while the engine is warming up. They also flow more easily any time your oil temps are below 100C - the standard test temp for engine oils. It can take 10 miles for the oil to come to an equilibrium temp - especially in cold weather. I have studed the Maxima data fairly closely and it is difficult to draw many conclusions, since there are so many uncontrolled variables (driving conditions, mechanical condition of different engines, miles on each sample, etc). The wear rates for the Mobil 1, 5w-30 and 10w-30 look pretty much the same if you go by that data, which is the most important thing. One of the more interesting things about the baseline data is that several of the API licensed synthetics, including Castrol Syntec and Valvoline Synpower, don't meet the 1000 ppm limit for phosphorus! TooSlick
 
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Jason, My recommendations are very simple ...I basically recommend the Amsoil product and drain interval I'd use if I owned your vehicle or piece of equipment. I don' t care what grade of oil you use, just that you get the best long term results. I have some customers who are uneasy about running a 0w-30 synthetic, so I sell them the 10w-30 and they are happy with that. It is sort of hard to make a bad recommendation with Mobil 1 or Amsoil, unless the oil is totally unsuited for the application (ie running a gas engine oil in a HD diesel). Ted
 
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