What is the weight of oil if I had to mix it?

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Is it as simple as math? Let's say the engine takes 5qt of 5-30. The weight of the oil in the engine is 5-30. If I was to add 1qt of 0-30 and 4qt of 5-30, is the weight of the oil now 4-30? Does oil blend like that or the different weigh of oil in the engine remain "separated?"
 
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MolaKule

Staff member
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A 0W30 will simply have a lower viscosity at 40C degrees than a 5W30 or 10W30. The lower viscosity at 40C should help cold weather starting and a faster oil supply. Here is a typical viscosity spec for 0W30: Viscosity @ 100°C 11.3 cST Viscosity @ 40°C 58 cSt Viscosity Index 193 RLI 0W30 This chart shows API "grades" verses actual Kinematic viscosity: http://www.bobistheoilguy.com/viscosity-charts/
 
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28,123
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Regina, Saskatchewan, Canada
Originally Posted By: cabanalane
If I was to add 1qt of 0-30 and 4qt of 5-30, is the weight of the oil now 4-30?
In addition to Mola's point, an oil either passes the 0w-xx requirements, or it doesn't, or it passes the 5w-xx requirements or it doesn't. So, the mix is either a somewhat different 5w-30 or a somewhat different 0w-30, assuming that something didn't mess up the cold cranking properties of the oil.
 
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Originally Posted By: Donald
Why?? Read to your kids, watch a movie, take the wife to dinner, forget about mixing oil.
Exactly... It's not like every grade/flavor/brand isn't at the store right now waiting for you.
 

cabanalane

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Cali
As to the why question? I have 3 cars that use 3 different weight of oil. I generally don't stock them at home. If I'm out or short, I'll use what I have. I guess it's better to go 0-30 if I don't have enough 5-30? In reality, I may add 1/4 qt to top off. From what I have searched and read, it's ok. And have been doing that (when I'm out). But just wanted to know if that actually changes the weight of the oil. Or there may be time when I got some 0-30 left, and if I'm doing an oil change, I may just use it up. To make the math easier, I set up the question that way. No, I don't mix the oil on purpose. So is it the "general" rule to go lighter? Meaning, I can add 0-30 to my 5-30 engine, but I should not add 10-30 to my 5-30 engine. Correct? I'm a newbie - so I'm sure this has been discussed a million times here.
 
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Chicago, IL
Originally Posted By: cabanalane
As to the why question? I have 3 cars that use 3 different weight of oil. I generally don't stock them at home. If I'm out or short, I'll use what I have. I guess it's better to go 0-30 if I don't have enough 5-30? In reality, I may add 1/4 qt to top off. From what I have searched and read, it's ok. And have been doing that (when I'm out). But just wanted to know if that actually changes the weight of the oil. Or there may be time when I got some 0-30 left, and if I'm doing an oil change, I may just use it up. To make the math easier, I set up the question that way. No, I don't mix the oil on purpose. So is it the "general" rule to go lighter? Meaning, I can add 0-30 to my 5-30 engine, but I should not add 10-30 to my 5-30 engine. Correct? I'm a newbie - so I'm sure this has been discussed a million times here.
I believe you've got it. The second number, the 30, describes the viscosity while at operating temperature, so in essence, all your vehicles that want xW-30 have the same viscosity when up to temp. The general rule, like you said, is that you can easily go lower in the winter rating. It might even be preferred in colder climates. If all your vehicles want xW-30, I would suggest stocking and using 0W-30 in all of them and sleeping well at night. Just noticed that you're in California. Wanted to add a note that in your climate, unless you're up on a mountain, even on your coldest days, the difference in viscosity between a 0W, 5W and 10W is relatively small (compared to the difference at 0F). I would still just use the 0W, but sleep even better at night.
 
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28,123
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Regina, Saskatchewan, Canada
Originally Posted By: cabanalane
I have 3 cars that use 3 different weight of oil. I generally don't stock them at home. If I'm out or short, I'll use what I have.
It might help if we knew the applications and oils to which you refer. After all, there are a few varieties of 0w-30 and 5w-30, some of which are in different service categories or meet different manufacturers' specifications. Syntec 0w-30 (GC) and M1 AFE 0w-30 and Delvac Elite 222 0w-30 are three rather different oils, for instance, with one being an A3/B4 type oil, one being an SN/GF-5 oil, and one being a CJ-4/SM HDEO.
 

cabanalane

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Cali
Mostly for two of the cars. 2002 Nissan Sentra QR25DE. 5-30. From what I read, owners seem to using all sorts of oil from 0-30, 10-30, and even 40 oils. I'm asking because these engines are known for timing chain rattles. Some say to use products like Lucas. But I read that it increase fuel pump pressure. So others suggested, perhaps a thicker oil. 2010 Honda Accord J35 V6. 5-20. Honda switched to 0-20 in 2011, same car, same engine. My 2014 Odyssey runs on 0-20. So figure maybe I should stock more of 0-20 since it seems like I can use it for both cars. The 0-30 car belongs to my father.
 
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Regina, Saskatchewan, Canada
What kind of a 0w-30 car does he have? The Sentra, given the vintage, would be perfectly comfortable on any 5w-30, not to mention any 0w-30 out there, be it ILSAC rated, GC, or an HDEO. As for Lucas, you're not going to find a lot of support for its use here, at all.
 
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