does the xW number even matter anymore?

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for a standard 3k 3month oil change interval, wouldnt it make most sence to run a 0wxx no matter what climate you are in? the only reason i can think of to use a higher cold number is for an engine which develops sludge quickly. as a 10w30 will not sludge as easily as a 0w30 for example, because the 0w30 has more VII's than the 10w30. am i correct in assuming these 2 things?
 
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When and if I run an oil with a 0w, more VI's, I am going to run a maintanence dose of Rx with it. Your right though, the spread is more ideal at a smaller amount like a 10w-30.
 
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You run a higher cold number because you can eg. you live in Hawaii and it's never below 50F. As far as the sludge issue...I had much more with a 5-30 than a 5-40. I don't think it's a VI issue as much as it's the oil breaking down because it was too thin to begin with.
 

cryptokid

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quote:
You run a higher cold number because you can eg. you live in Hawaii and it's never below 50F.
although i used to go by that logic, i dont think i will anymore.
 
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Why not? I live in Toronto and a grade such as a 5-50 would be more appropriate for year-round use compared to say, Hawaii or Australia where one could comfortably use a 20-50 all year because extreme cold is not present in these places.
 
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quote:
Originally posted by Dr. T: As far as the sludge issue...I had much more with a 5-30 than a 5-40. I don't think it's a VI issue as much as it's the oil breaking down because it was too thin to begin with.
Yes, Large spread and VII's, tend to result in extra varnish. Extra sludge comes from running an oil that is either too thin or too low a quality. Fred... [Smile]
 
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