Why does my car indicate 5W-30 is good year round oil but many viscosity charts say it's only best under 60F?

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I live in a warm climate and always used 5W-30 because my owner's manual said it's the best for fuel economy. However, from looking closer at charts it looks like 10W-30 is for 0F+ and 5W-30 should only be used for 60F below.

Why the discrepancy?
 
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Sounds like what my 300ZX's fsm says. 5W30 only under extreme cold. 10W30 up to 60F and 60F and above use 10W40.
Same thing with the Legend. I run a 15w-40 HDEO.
Engine-Trans Lube Viscosity Requirements.jpg
 
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You viscosity chart is for API SF oil... SF was in effect as the latest and greatest thing between 1980 and 1988. At that time, technological development of VII (viscosity index improver) was still in its infancy - a typical conventional oil 5W30 would have too much shear in the 3000 mile typical oil change interval, and would likely finish as a thinner 5W20, causing more wear than 10W30 (which would use less VII, thus shearing less) in temperate and hot temperature (above 0°F) usage.

Oil has improved tremendously since then.
 
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I live in a warm climate and always used 5W-30 because my owner's manual said it's the best for fuel economy. However, from looking closer at charts it looks like 10W-30 is for 0F+ and 5W-30 should only be used for 60F below.

Why the discrepancy?
Just run the 5W30 and forget about it. That’s what my Tacoma calls for and runs great in the southern heat. 0W20 is used in my wife’s Pilot…same result.
 

Puhdantic

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You viscosity chart is for API SF oil... SF was in effect as the latest and greatest thing between 1980 and 1988. At that time, technological development of VII (viscosity index improver) was still in its infancy - a typical conventional oil 5W30 would have too much shear in the 3000 mile typical oil change interval, and would likely finish as a thinner 5W20, causing more wear than 10W30 (which would use less VII, thus shearing less) in temperate and hot temperature (above 0°F) usage.

Oil has improved tremendously since then.

My FSM chart lists the oil specs with grade SH in mind. While in the owner's manual it lists the specs with SJ in mind.

So maybe the specs in the FSM were written prior and then when they made the owner's manual, they updated it to refelect that.

What this leads me to understand is that a facet like oil startup temp range can become more varied and all encompassing as improvements are made to it. Better yet, these temperature viscosity chart ranges change as new API standards come up.
 
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My FSM chart lists the oil specs with grade SH in mind. While in the owner's manual it lists the specs with SJ in mind.

So maybe the specs in the FSM were written prior and then when they made the owner's manual, they updated it to refelect that.

What this leads me to understand is that a facet like oil startup temp range can become more varied and all encompassing as improvements are made to it. Better yet, these temperature viscosity chart ranges change as new API standards come up.


The API designations have nothing to do with viscosity and grade.

I will defer to the more knowledgeable members here to explain it fully.
 

Jackson_Slugger

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What car is it? Carbureted or FI? High horsepower or marginal by today's standards? The current syn 5W-30's will generally be better than the SF 10W-30s...
 
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My FSM chart lists the oil specs with grade SH in mind. While in the owner's manual it lists the specs with SJ in mind.

So maybe the specs in the FSM were written prior and then when they made the owner's manual, they updated it to refelect that.

What this leads me to understand is that a facet like oil startup temp range can become more varied and all encompassing as improvements are made to it. Better yet, these temperature viscosity chart ranges change as new API standards come up.
Which are you worried about? The winter rating or the operational viscosity? They are two separate things and aren’t really related. The fact remains that an oil with a 5W winter rating is suitable for starting down to about -30 or so. The operational viscosity (or better the HT/HS) is what controls wear. As long as it is somewhere around 3.0 it will be suitable for nearly any “regular” engine. There is no downside to a somewhat higher HT/HS except for somewhat lower fuel economy.

API licenses are all backwards compatible so you can use an oil with an API SP license.
 
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I live in a warm climate and always used 5W-30 because my owner's manual said it's the best for fuel economy. However, from looking closer at charts it looks like 10W-30 is for 0F+ and 5W-30 should only be used for 60F below.

Why the discrepancy?
5W30 is most like a synthetic 10W30 probably not I'd use 5W30 you gain nothing with the other viscosity.
 

Jackson_Slugger

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I'm guessing you have the 2.7L V6, and I was assuming with the archaic SF, even the listed SJ was out of date and should be SM IIRC. The SF rating that we were talking about is something from the 90's. The Kia V6 only pushes out about 175HP and they tended to be durable. Any 5W-30 will be fine, with some actually being thicker at op temp than many 10W-30's...
 
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I live in a warm climate and always used [ 5W-30 because my owner's manual said it's the best for fuel economy] . However, from looking closer at charts it looks like 10W-30 is for 0F+ and 5W-30 should only be used for 60F below.

Why the discrepancy?
Corporate Average Fuel Economy.
 
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