5w30 vs 10w30

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my boss doesnt know which end of a hammer to hold but he knows better then to question what his car needs when it breaks. But the other day he went to the local castrol place and the head guy there told him to get 10w30 instead of 5w30. he was kinda puzzled but when the guy said (its Africa hot here, you know that) he agreed and got the 10w30....

last year the coldest day was 30 degrees, and i think it was the only day under 40 degrees. its over 100* normally and peaks at ~117* or more.

do i ( in general) need to worry about cold start ups? i usually let the trucks idle for about 30 seconds befpre dropping them into gear.

on another note, is 10w30 stronger (other then being a 10 wt and different flow rate) then 5w30?

i have 3/4 things in my head that are conflicting, like the specs some owners manuals ive seen in the past for cold starts and or oil weights being much stronger today
 
In theory a mineral 10w30 should have less viscosity index improvers than the mineral 5w30, so it should stay at starting viscosity longer than the 5w30, but most engines won't shear a API SN 5w30, although i have seen it before.

If we are talking about synthetics, theres almost no reason to use a 10w30 synthetic over a 5w30 synthetic unless you want an oil with ZERO VII's which is what a 10w30 syn usually is, since the base oil flows so well you don't need extra VII to get the 10 winter rating. This is why you see Amsoil market their small engine oil as 10w30/SAE 30 synthetic, since it flows well enough to get a 10w30 grade but has no VII.

In AZ heat, there won't be much difference, since at 30F, the 10w30 will flow okay still, but anything near 0F the 5w30 is preferred.

Prepare for many opinions on this matter too.
 
10w30 is good for cold starts down to -30C (-22F). It wouldn't be a problem at 30F. Letting your truck idle for 30 seconds before putting it in gear is a reasonable precaution to assure that oil has pressurized the farthest reaches of the oil system. Any more time than that, and you're just wasting fuel.

As a very broad general rule, 10w30 oils have more resistance to shear viscosity loss than 5w30's. But that doesn't necessarily mean that all 10w30's are "stronger" than all 5w30's. "Strong" can mean different things when applied to oil. Is it shear resistance, viscosity, long life, or anti-wear that you are concerned about?
 
Search this topic, is has been discussed ad nauseam.

A decade ago 10W-XX multigrade (no such thing as "weight"; W= all seasons Winter use) was a more robust oil than a 5W-XX and made less sludge.
Today I see it used more in air cooled ODPE or med duty gasoline engine delivery trucks, certain road racing applications or as a vintage car oil. 10w-30: That's the 'GRADE' now you have to spec the service category to make a complete application.

You are fine with the 10w30 in a med duty truck if 30 is the correct grade for your temps and you also have the right service category. Are these gas or diesel? I would assume gas, no?
 
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There is no need for 10w30 with today's oils. You have nothing to benefit other than fewer VI's which is virtually irrelevant with almost every SN oil as they don't shear like they used too. The only reason I am running a 10w30 in the Uplander now is because it was a full synthetic EP oil on clearance at WM for $15, and it will be drained before the cooler weather rolls around. 5W30, the recommended weight will be going in.
 
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Originally Posted By: A_Harman
10w30 is good for cold starts down to -30C (-22F). It wouldn't be a problem at 30F.


I would cringe turning the key with mineral 10w30 in the sump @ -22F!
 
Originally Posted By: gregk24
The only reason I am running a 10w30 in the Uplander now is because it was a full synthetic EP oil on clearance at WM for $15, and it will be drained before the cooler weather rolls around. 5W30, the recommended weight will be going in.


Cooler weather rolls around?
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Are you in northern FL Greg?
 
Once (1997) in a trip from LA (USA) to SP (BRAZIL) I bought a BUNCH of cheap monograde sae 40 (straight 40) in Mexico (Nogales) for my former GM Veraneio with a Turbo Diesel Perkins and, when at or below 36F (winter), the engine clacked for about one block or 2 (half mile at most) and did no harm, in spite of the annoying noise at warmup. Got 20k miles on that trip + 50 more until sold. Sure I was kindda easy white the thing made knocks but it made ok.
 
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From a practical standpoint, 5W-30 vs 10W-30 probably won't matter much in Arizona. While the 5W-30 will have marginally better performance in the 'cold' temperatures you'll encounter in AZ, the 10W-30 (assuming the same brand and type) will likely have a lower NOACK volatility which would (theoretically) reduce oil usage, and would also (theoretically) be more shear-stable.

I would certainly not hesitate to use 5W-30 year-round, but assuming multiple oil changes per year (and assuming equal availability and cost) I'd opt for 10W-30 in the summer, where the theoretical benefits are most likely to outweigh the marginally worse 'low temp' characteristics at your typical summertime startup temperatures.
 
Originally Posted By: gregk24
The only reason I am running a 10w30 in the Uplander now is because it was a full synthetic EP oil on clearance at WM for $15, and it will be drained before the cooler weather rolls around.


I am so glad you drained that awful synthetic 10-30 out before that brutal Florida winter sets in. Who knows? It might even get down to 50 degrees for an hour or so, and your poor engine would be locked up solid with that thicker than molasses 10-30 in it.
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Originally Posted By: gregk24
There is no need for 10w30 with today's oils. You have nothing to benefit other than fewer VI's which is virtually irrelevant with almost every SN oil as they don't shear like they used too. The only reason I am running a 10w30 in the Uplander now is because it was a full synthetic EP oil on clearance at WM for $15, and it will be drained before the cooler weather rolls around. 5W30, the recommended weight will be going in.


You don't have anything to gain dropping the 10W30 for your cooler weather., but if it makes you feel better about it, then it's all good.

5W30s have about the same VII additive treat rate as a 10W40 (about double that of a 10W30)...roughly 10% of a dino 5W30 is VII additive versus 5% for a 10W30 as per Afton's product data sheets....I'm assuming that the OPs boss wasn't getting synthetic.
 
I've seen everything now. Some guys want to use 10w-30 down to -30 C and others want to change it out before the "winter" hits Florida.
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I suppose we've got a wide spectrum of suggestions here.

Personally, I'd tend to avoid the 10w-30. However, I wouldn't worry about it in a Florida winter, but I wouldn't try starting with it in -30 C, either, unless I had some "help" such as an oil pan heater.
 
Why cant we just use COMMON SENSE and use whats appropriate for the climate? Use 0-X and 5-X oils in the snow belt, and use 10-30 across the Gulf Coast?

Dang, I used straight 30wt. one "winter" in SETX with ZERO issues. To fear a synthetic 10-30 in Florida is beyond ridiculous.
 
Wouldn't "common sense" dictate to just use what the book and cap say?

Myself, I don't think there is to be gained with the 10w30 either. I also don't think you're going to bring a premature end to your engine if you decide to use it either.
 
Originally Posted By: cp3
Wouldn't "common sense" dictate to just use what the book and cap say?


Actually, CAFE dictates what is on the cap and in the book.

One day, the casual user might understand this, but I would not bet on it.
 
Despite being out of vogue here 10w30 works well in just about anything. In AZ I'd never give it a second thought and you will never know the difference.

Now Canada....
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Originally Posted By: cp3
Wouldn't "common sense" dictate to just use what the book and cap say?


Yep, in Oz, the cap almost invariable says "oil", or has a picture of an oil can.

The manuals have handy charts to look up what's appropriate for operating conditions.

It's really that easy.
 
Originally Posted By: Shannow
Originally Posted By: cp3
Wouldn't "common sense" dictate to just use what the book and cap say?


Yep, in Oz, the cap almost invariable says "oil", or has a picture of an oil can.

The manuals have handy charts to look up what's appropriate for operating conditions.

It's really that easy.


Indeed. As long as one doesn't get that little "oil" symbol confused with the international symbol for "wiper fluid", it's not going to make a huge difference...
 
Originally Posted By: gfh77665
Actually, CAFE dictates what is on the cap and in the book.


Wait...I thought we were talking about what oil to use not who dictates what's on the cap and in the book?

Originally Posted By: KCJeep
Now Canada....
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RIGHT! I wouldn't use that goop up here! I'd not make it to work for half the year!

I'd have to be like my buddy who uses that s**t in everything! He finally bought a car that calls for it. Yep even up here!
 
Originally Posted By: Shannow
Yep, in Oz, the cap almost invariable says "oil", or has a picture of an oil can.

In Canada, that's pretty much the norm, too, but some will have a viscosity listed. My old truck has some weird verbiage placed somewhere under the hood with warnings about oil choice. I'll have to get a picture of it or at least write the gist of it down so I can share it here one of these days.
 
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