In current name brand oils is there any reason not to always use 5 W30 instead of 10 W30?

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With modern oils is there any reason not to always use the lowest cold rating with the same operating temperature rating oil? I have read that in the past 5 W30 oil had more additive and was less shear stable than 10 W30 but does that still apply today? Also even if my manual doesn't mention it, because it wasn't invented in 1992, is they any reason not to use 0 w30 oil in a car that calls for 5 or 10 W30 oil. It is my understanding that the first number is the viscosity when cold. Why not use the lowest cold rating while keeping the "hot" rating?
 
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Most 5W's are thinner than their 10w counterparts when hot, but still a "30". So that sways some people that want a slightly thicker oil.

Beyond that, I agree with your assumptions.
 
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10w-30s in the same brand and lineup are typically better and some 10w-30's are slightly thinner in the kv100 to try to close the gap of the viscosity index. 10w-30's almost always have less volatility and a higher hths because of the lower viscosity index from having less viscosity improvers.. I'll typically use a 10w-30 before a 5w-30 unless it's a special case. Castrol edge 10w-30 has an impressive noack of 6.6%.

valvoline full syn hm 10w-30 is 10.8 but with an hths of 3.3 while the 5w-30 is 10.5 but 3.1. But QSFS 10w-30 is thinner than 5w-30 while having a higher flash point as well and probably a slightly higher hths although the shell docs don't list that like Valvoline.
 
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It'd depend on modifiers in the oil, I watched a video where they tested an oil in Europe that actually got a tad thicker (1.2% or so) during shear testing. I will be trying 0w-30 C2/C3 oil in the future when running out of my little stock.
 
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10w-30s in the same brand and lineup are typically better and some 10w-30's are slightly thinner in the kv100 to try to close the gap of the viscosity index. 10w-30's almost always have less volatility and a higher hths because of the lower viscosity index from having less viscosity improvers.. I'll typically use a 10w-30 before a 5w-30 unless it's a special case. Castrol edge 10w-30 has an impressive noack of 6.6%.
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I agree and use 10w30 where 5w30 is recommended, unless I'll be doing frequent starts in sub-freezing temperatures. Over the years I've gotten great UOA results from cheap 10w30 oils, good for extended drain intervals.
 
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I agree and use 10w30 where 5w30 is recommended, unless I'll be doing frequent starts in sub-freezing temperatures. Over the years I've gotten great UOA results from cheap 10w30 oils, good for extended drain intervals.
valvoline FSHM 10w-30 is pretty good because of the additive pack at 960zinc and 800ph and the 3.3 hths at 10.8 kv100. Castrol pds's say 6.6% noack on their 10w-30. Quaker state's 10w-30 syn also looks great. Really like them and they all flow just fine in the cold unless its ridiculous outside.
 

FZ1

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With modern oils is there any reason not to always use the lowest cold rating with the same operating temperature rating oil? I have read that in the past 5 W30 oil had more additive and was less shear stable than 10 W30 but does that still apply today? Also even if my manual doesn't mention it, because it wasn't invented in 1992, is they any reason not to use 0 w30 oil in a car that calls for 5 or 10 W30 oil. It is my understanding that the first number is the viscosity when cold. Why not use the lowest cold rating while keeping the "hot" rating?
Agree. Go with the flow. Most wear occurs on start up. It's cold up there in Mi.
 

SR5

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A 10W30 is good down to 0F (-20C), below that temperature use 5W30 for better starting.

Don't be fooled by better "flow" from a 5W30 or 0W30 compared to a 10W30 at warmer temperatures, once warm they are all pumped fine and they are all pumped the same. The oil in your car is pumped, not gravity fed.

Comparing a 5W30 to a 10W30, formulated the same and from the same company, for a warm climate I would always select the 10W30. A 10W30 would use less polymer VII and so be more shear stable, and would use thicker base stock and therefore have a lower Noack volatility. Both advantages.

The 5W30 above is selling Noack & Shear Stability to buy cold starting (expressed in the W winter rating). But if you are selling something that is good for something you don't need (in a warm climate) then I see it as a poor deal.
 
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Excellent threads, posts, and replies.

I have always wondered the same, and we have a clear and concise thread and replies talking about why 10W is preferred.

Thank you.
 
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With modern oils is there any reason not to always use the lowest cold rating with the same operating temperature rating oil? I have read that in the past 5 W30 oil had more additive and was less shear stable than 10 W30 but does that still apply today? Also even if my manual doesn't mention it, because it wasn't invented in 1992, is they any reason not to use 0 w30 oil in a car that calls for 5 or 10 W30 oil. It is my understanding that the first number is the viscosity when cold. Why not use the lowest cold rating while keeping the "hot" rating?
My personal feeling is I use which ever one is cheapest. Sometimes it 5W-30 sometimes it 10W-30. Price point is king in this house.
 
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Agree. Go with the flow. Most wear occurs on start up. It's cold up there in Mi.
Well yeah startup since there's basically nothing on the parts aside from like atoms worth of oil film on the contact surfaces like overhead cams and caps. At startup some engines fly just past 1500rpms before slowly going down so imagine having zero oil pressure for a few seconds. Engines like in my trucks can take 3-5 seconds to get the oil pressure gauge to finally stop climbing. Even then some parts maynt be fully lubricated.

Best thing you can do no matter the climate or engine is to let the engine idle for 5 seconds before putting a load on it or taking off because some cars have lower pressure pumps and take longer still.
 
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My personal feeling is I use which ever one is cheapest. Sometimes it 5W-30 sometimes it 10W-30. Price point is king in this house.
I agree. If I'm gonna spend bygone $15 bucks on supertech syn i might as well get the one with the highest hths so I'll just get the 10w-30 over the 0w-20. Same cost better product. A syn 10w-30 will still flow just fine down to 0f which it never gets to here anyway.
 
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With modern oils is there any reason not to always use the lowest cold rating with the same operating temperature rating oil? I have read that in the past 5 W30 oil had more additive and was less shear stable than 10 W30 but does that still apply today? Also even if my manual doesn't mention it, because it wasn't invented in 1992, is they any reason not to use 0 w30 oil in a car that calls for 5 or 10 W30 oil. It is my understanding that the first number is the viscosity when cold. Why not use the lowest cold rating while keeping the "hot" rating?
Unless you live in a northern Winter here is no reason TO use a 5w-30 over 10w-30.
All other things being equal a 10w-30 will be n=more oxidation resistant, less varnishing and run longer than a 5w-30.
Having said all the those differences are a bit academic as modern oils are so good 5w-30 especially synthetic ones are often quite stable.

But unless you are worried about pumping oil in the negative degree range no reason to go to 5w-30 except fuel economy in the minutes during warm up.
The EPA cycle is heavily biased towards this, which is the sole reason we see the trend to thinner oils.
 
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In general, if the W # meets your cold temp requirements:
Narrow spread = Less plastic
Which is good.

However, 0W oils have a better base oil ... and you have to be careful what you are buying when buying 10W. For example I like M1 EP 10W-30 but prefer a 0W over inferior 10W-30s like dino or syn-blend.

With 10W, they can dump a dino or blend on you but with 0W you get a better oil without much needed research. Meaning when you buy a 0W, they can't dump a cheap dino or blend on you.
 
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In general, if the W # meets your cold temp requirements:
Narrow spread = Less plastic
Which is good.

However, 0W oils have a better base oil ... and you have to be careful what you are buying when buying 10W. For example I like M1 EP 10W-30 but prefer a 0W over inferior 10W-30s like dino or syn-blend.

With 10W, they can dump a dino or blend on you but with 0W you get a better oil without much needed research. Meaning when you buy a 0W, they can't dump a cheap dino or blend on you.
Several 0w-20 car manufacturer oils (Toyota, Mazda, Nissan) have very high VI and high Noack. What do you think of the base oils used?
 

FZ1

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Well yeah startup since there's basically nothing on the parts aside from like atoms worth of oil film on the contact surfaces like overhead cams and caps. At startup some engines fly just past 1500rpms before slowly going down so imagine having zero oil pressure for a few seconds. Engines like in my trucks can take 3-5 seconds to get the oil pressure gauge to finally stop climbing. Even then some parts maynt be fully lubricated.

Best thing you can do no matter the climate or engine is to let the engine idle for 5 seconds before putting a load on it or taking off because some cars have lower pressure pumps and take longer still.
Agree. I fire it up and wait 30 seconds or so till the start up revs begin coming down, then, drive slowly. I have mostly short trips so my oil is not up to operating temp, on most occasions, so I prefer to go with the flow vs. thicker. M1 0w-20 AFE runs nice in my 17 Camry. It's an 8.8 viscosity so not too thin for my use. Jmo
 
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FZ1

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Unless you live in a northern Winter here is no reason TO use a 5w-30 over 10w-30.
All other things being equal a 10w-30 will be n=more oxidation resistant, less varnishing and run longer than a 5w-30.
Having said all the those differences are a bit academic as modern oils are so good 5w-30 especially synthetic ones are often quite stable.

But unless you are worried about pumping oil in the negative degree range no reason to go to 5w-30 except fuel economy in the minutes during warm up.
The EPA cycle is heavily biased towards this, which is the sole reason we see the trend to thinner oils.
The op lives in Michigan. I here it gets pretty cold, up there.
 
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Several 0w-20 car manufacturer oils (Toyota, Mazda, Nissan) have very high VI and high Noack. What do you think of the base oils used?

I try to use 10W-30 whenever possible. In general I like oils with low vm (vii) & low Noack.

I have used M1 EP 10W30 and some GTX Magnatec Full Syn 10W-30 and in the past Chevron Supreme 10W-30 (dino) but now I only use M1 EP when it comes to 10W.

Recently I bought some 5W-30 Kirkland for the price.
Never bought any xW-20 despite the fact that 2 of our cars specify 0W-20 and 5W-20 ... Too thin for me (maybe not for the engine! lol) But for example if I was forced to choose between 10W-30 dino or TGMO 0W-20 for my Tundra, I would take the 0W-20 which is also the recommended viscosity grade.

TGMO 0W-20 is supposed to be (or used to be) very good with lots of moly but I think that has changed.

The only 0W that I've ever bought was last year for a summer trip with a loaded car and I bought some M1 FS Euro 0W-40 and Casterol A3/B4 0W-40. I basically wanted a good 40 oil since the 0 is not relevant in the summer and was easy to find those in store.

Some experts claim that high(er) amounts of vm (vii) are not that bad and won't shear ... but I still try to avoid it.
 
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