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And to state that the "W" has to do with winter, that's bending a bit. A lower viscosity or "weight" is used in colder climates sot the oil can flow, as stated by dirtbikindad, and as the engine warms, it gets thicker, and in this case, becomes 40 weight.

The numbers have nothing to do with outside temps, meaning 5 weight flows at 5 degrees. If that were the case, I'd have to run 90W gear oil in my engine during the Florida summers when its 98+ degrees outside.
 

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If that were the case, I'd have to run 90W gear oil in my engine during the Florida summers when its 98+ degrees outside.
You'd probably have no issue running a 40 straight weight tbh.

There's just so much wrong in this thread.
5w-40 has a broader operating range than 15w-40. Unless you're penny pinching or you're misinformed about synthetic oils, it's stupid to pick the 15w-40 option.

There is a single benefit to 15w-40 oils though, they will maintain their 40 weight operating viscosity longer than an oil that starts at 5w. This is not rocket science, it takes less friction modifiers to get from 15 to 40 than it does from 5. This ONLY comes into effect when oil is used past the 10k mile point or is being used in severe duty.

You guys are over thinking this WAY too much.
 

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You guys are over thinking this WAY too much.
true!

original thread question, "Hey guys and girls, just wondering what the difference is between 5w40 and 15w40? I have a 2002 chevy with 170000km on it and about to put amsoil in just not sure what to get cause I don't know the difference. Can anyone please help out."

---Lower "w" works better when colder:smile2:
 

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Ams offers Syn in both 5w and 15w, IIRC.
 

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Discussion Starter · #28 ·
to ad to this:
The letter following the first number "w" has come to be called "weight" but it is not actually, it stands for "winter". This is the lowest temp that it will flow at. 5w40 Is at 5 degrees it will flow and anything colder will make it flow less. Likewise 15w40 is at 15 degrees is the lowest it will flow at.

The "weight" of the oil is found on the label and is usually listed in Once, Quarts, or Gallons (liters outside the USA).

The second number is the Viscosity this is what you consider for your driving engine temp. This will vary depending on your engine, unless you have a built LB7 with tight tolerances the 40 is all you will need.

Just wanted to point this out as it helps to understand your oil and running the right oil for your region.

For most trucks a 5w40 is a safe oil

I run a 0w40 for where I live due to temps hitting -20 and lower in January. It only matters really if the truck sits somewhere to cool off enough to get to ambient temp. If you have a block heater or park in a heated garage not that big of a deal.
So because I live in ottawa canada and it does tend to get colder then -20 in January, and I'm thinking of changing to 5w40 synthetic because of it. Would it hurt anything by running 5w40 synthetic in the summer instead of changing my oil back to 15w40 synthetic?

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Discussion Starter · #30 ·
At operating temp is almost essentially THE EXACT SAME OIL!!!! 40 weight!!!!
Yes I underatand that. But having a 5w in the summer will only be that must easier on it to start, and not change start up? I'm not trying to be rude or anything. When I first got the truck I got fucked around on injectors for $10k I want to be 100% on everything from here on in. I appreciate everyone's input and explaining everything about oil.

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I run Schaeffer's 9000 full syn 5w40....in Texas triple digit heat.
You'll be a'right. :farmer
 
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wow there are some interesting opinions in this thread.



5-40 does not make your truck leak, if your truck leaks after you put 5-40 in then your engine was already worn out.

5-40 is thinner in the cold. there is no need to run 5-40, however those who live in cold climates that frequently get below 0 may experience easier starting, less wear and tear on the engine, and quicker warm up times with 5-40.
 

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Oil threads such as this always lead to misinformation, hence the reason for all the posts.

When ever in doubt, follow the advice of your owners manual. It will state the recommended viscosity range to use based on your climate area.
 

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I do what my dealer recommends, tx is always 15w40


2004 Silverado LT LB7

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So because I live in ottawa canada and it does tend to get colder then -20 in January, and I'm thinking of changing to 5w40 synthetic because of it. Would it hurt anything by running 5w40 synthetic in the summer instead of changing my oil back to 15w40 synthetic?

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Short answer............Not at all
 
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Filters is a whole other argument.

Touching on the oil debate (cause I like to poke bee nests lol) I've only ran 0w oils in my vehicles. My truck runs 0w40, my wife's truck is 0w20. I see temps anywhere from around -40 to almost +40c some summers (38 or 39 this year). Ever gone into the bulk suppliers? Local shop has a demo with 4 or 5 types of oil with ball bearings. Room temp, the 0w ALMOST falls through the oil like water. This is the advantage of a 0w or 5w in colder climates, though they are just as beneficial in warmer ones. You see, that 0w oil can start lubricating much quicker then the 5 or 15, while still being a 40 once engine temps are up.

I've never seen a 0w as anything but an engine saver just for its ability to quickly lube the engine on start up, whether it's due to cold temps or just sitting a while.
 

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Oil filters I did a write up on Diesel Place on micron ratings and what to look for. It can be found here for the full article.

Microns (mics) are a measure of how wide a particulate is. To give you a idea of how it works, a typical human hair from your head is approx 40-50 mics wide.
Long story short is there are two micron ratings used by the manufacturers.
They are "Nominal" which is what the filter can trap 50% of the time (who cares what the filter can trap 50% of the time) and the true number that really means anything is the "Absolute" number. The Absolute number is what the filter can trap 97-99.9% of the time, this is the number you want to know when choosing a filter. Nominal is used by many companies as the number used in marketing material because its a smaller number and looks better. You want to know what the "Absolute" number of your filter choice is if you care about longevity.

What is the best filter to use? The answer is personal and depends on how much a person wants to spend for protection. IMHO don't be penny wise and dollar foolish when it comes to filtration and oils.
Examples;
The factory AC Delco PF2232 filter is a 40 micron filter, Wix 57202 37 mic, the Baldwin B1441 is a 28 mic filter and the Amsoil EAO52 is a 20 mic filter (all absolute numbers).

Its no surprise what I use on all of my vehicles the Amsoil filters. My Duramax has a dual bypass on it so the full flow filter is 20 mic (absolute) the bypass is 2 mic (absolute).

This post is not meant to start a filter battle. It is merely information as I know it for you the reader to digest for your research.
 
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