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high mileage oil weight?

62810 Views 18 Replies 9 Participants Last post by  Truck Guy
I have a 2011 silverado 5.3L which I got around 80k miles. Ive been running Pennzoil Ultra Platinum 5w-30 Synthetic since I got it. I was looking into running a high mileage synthetic like mobile 1 high mileage full synthetic but wasn't sure If I should stick to the factory recommended 5w-30 or Ive read that some people change the oil weight in high mileage vehicles. What do you think? I have about 97k miles on it now.

Thanks in advance for your suggestions.
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Are you experiencing something that is causing you to consider a oil viscosity change? If you are getting good results with what you are using, why change? I have never changed the viscosity of the oil throughout the entire life cycle of any engine I have owned. From the 1974 Pontiac Catalina with a 400 small block that I finally got rid of at 267,000 miles, to the 2 semi trucks that I have taken to well over 1 million miles each on the same engine with NO rebuild or even a major engine repair.

Your engine is NOT high miles. I don't even consider a typical small block to reach the "high miles" category till over 150,000 miles in normal use. You are only 2/3 the way there! But if you are experiencing a significantly higher oil consumption, it might be an option, but doing that might just be masking a problem that will only get worse. A high mileage oil might help with some oil leakage from seals, but not if they are on their last leg. Pennzoil UP is a very solid oil. I would see no reason to go to anything else for quite a while.
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No problem with going with a less expensive product. Look at the Pennzoil synthetic blends. There is really no need to run a full synthetic. The blends from Pennzoil are stellar products. Heck, even the Wally World Superrtech branded oil is a good oil. It has gotten good reviews from some of the folks over at the BITOG website, which is a lubrication specific website. You have a myriad of options. Look for sales. For the 5.3L I would at least recommend a blend, and there are a lot of good quality synthetic blends on the market. Go with what your gut and your wallet feels right about.
That's right. also some additional oil seal elastomers to keep seals fresh. Seems like if you got a good deal on the Mobil 1, it should be a good choice. Good deals are always a good thing!
Keep in mind, the only difference between a 0w30, 5w30, or 10w30 is the winter flow rating. That is the number in front of the "w". Has nothing to do with operating viscosity. They are all 30w oils. There are even some straight weight synthetic 30w oils that also qualify as a 10w30 simply because, even though they are a straight weight oil, they meet the winter flow rating to qualify as a 10w30. If someone is primarily in a warm climate, they will have no problem using a 10w30 oil.

GM has to cover all the bases of the average consumer, so they are going to recommend a 5w30. I have no problem with that. But I wouldn't even use that in Fairbanks, AK in the winter! I would use a 0w30. If I lived in TX or the Gulf Coast states, I would not hesitate to use a 10w30 if it was a better value than a 5w30. Just look for the sales.
That would indeed be an issue if we were debating 20w vs 30w vs 40w oils. But 0w30 vs 5w30 vs 10w30 differences are simply winter flow rating, not a viscosity difference. Many folks, including those who should know better since it is their business, have misconceptions about this. The American Petroleum Institute is very clear on this.
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Let's take a look at the viscosity at 100c of a 0w30, 5w30, and 10w30 from a oil blender data sheet.....

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The ow30, 5w30, 10w30 all have the same viscosity at 100c / 212F operating temperature. Only the cold flow crank start rating at engine startup is different. But notice something else.... the NOACK (burn off vaporization rate) is higher for the 5w30 and 0w30 than the 10w30. It is because more viscosity improvers are needed to make them flow at colder temps than the 10w30. And along with more VI, there is the increased possibility of oil shearing under extreme pressure. To get something, you have to sacrifice somewhere else. The assertions that a 0w30 or 5w30 is better than a 10w30 because of tighter engine tolerances are not grounded in reality. All of these oils have the same viscosity in engine operation. Only the cold flow is different. And GM's recommendation, while not invalid, is out of their motivation to cover all the extremes as best they can and overcome the low brain wave activity of many consumers. If they didn't make the recommendation they do, there would be instances of consumers dropping in a straight 30w oil, which would probably mess things up in cold temps.
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As I stated, I did for the most part. They recommend a 30w oil. And that is what I use. We just differ on the cold winter flow rate, but I don't live in Duluth, MN in the winter.
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