Basic oil viscosity question

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Jul 1, 2004
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boca raton, florida
I was wondering if there are any hard studies that show whether there is any long term affect (positive or negative) in using a base 10W vs. base 5W oil. In a warm climate - where winter temperatures don't get colder than about 65 degrees F, does it really matter whether you use a 5W30 vs. a 10W30? The question is precipitated by the often recommended 5W20, 5W30 or even 5W40 oils that many modern cars specify. In the quest to maximize CAFE values, I question whether the base 5W makes a difference - especially in a warm climate. Thanks for your responses.
 
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The effect should be the same because the viscosity at higher ambient temps of both 10w and 5w oils should be around the same, its only at low temps that the viscosity is lower (5w) or higher (10w).... The only difference would be that the 5w may have slightly more vi improvers and sheer down a little faster, but with today's synth oils this is almost a non-issue as you have 0W-40 oils doing very well in sheer tests.... [ July 02, 2004, 10:34 PM: Message edited by: cweed ]
 
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