See my answer above, and then substitute engine for knowledge of the topic in the US.

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If 10w-30 is obsolete, then why is it the #1 used weight oil in the United States?
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I believe that 5w30's are better in every category.
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If 10w-30 is obsolete, then why is it the #1 used weight oil in the United States?
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If 10w-30 is obsolete, then why is it the #1 used weight oil in the United States?
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Diamler/chrysler is trying to get on the band wagon with Ford with the 5w20. Their cars and trucks always recommended a thicker oil. The 2004 and 2005 hemis called for 10w30 then bang no engine changes, just lets go with 5w20. Its a fuel savings ploy, whenever I looking for a truck, every Ford dealer would mention the bad fuel milelage with a hemi. Dodge is trying to shun this reputation a little. Anyway I use 5w30 and 10w30 in the hot summer months in Florida, I have a 2006 Hemi without the MDS(3/4 ton) and I will continue, I do have friends who are scared of the warranty and are using 5w20 and their trucks are using oil, not alot, but my uses none, Even on a long 1200 mile one way nonstop trip, not a ounce. I was at the Ford dealer where we bought my wifes car, and asked him about the 5w20 oil and the manager told me, we use it but if we get a customer in complaining about their car/truck using oil, we use the 5w30 and it stops any oil use. Also I would like to note they sell the same cars in Europe, but dont sell 5w20 there and most warranties there require 5w40. 10w30 is not like gear oil, its actually as thin as 5w30 was 5 years ago, so if engines got tighter, well oil got lighter.
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Again, if the manufacturers require a certain viscosity, then the oil companies must meet it. And we will buy it, at least in order to maintain warranty negotiations. Chrysler with the 3.5L, Kia requires a minimum 10W-40 in its Hyundai 3.5L, certain turbo applications want 10W-30 or thicker, etc. How can something be called obsolete when the manufacturers - working with the oil companies, I would think - require a grade thicker than 5W-20,-30? Sheez, I hope the manufacturers should be basing this on tests and results...
That's why you want to use a high mileage 10w30 that does not have "energy conserving" on the bottle. I have not seen Maxlife 10w30 sheer down.Quote:
But UOAs show us 10W-30 shearing down as fast (almost as fast?) as 5W-30s these days. I'm chalking this up to ecological pressure on the oil companies to make thinner oils to save fuel (on a macro level).
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I'd quess about a quarter of the US population probably lives in areas where a straight 30 grade would work fine (southern Cal, AZ, Texas, Gulf Coast, Florida, etc).