I have a 2003 1500 with a 5.9 magnum. The owners manual says to use 5w-30 oil when the temp is below freezing. And to use 10w-30 when temps are above 32 and higher than 80. The temps here are rarely over 80 and below freezing all winter.

I know that the 5w or 10w is the oil weight under cold conditions. so using 5w in cold weather will give better flow at start up. But shouldn't the 30 of both oils give the same viscosity under hot weather or full operating temps.

I have asked a couple mechanics and nobody can tell my why the 5w-30 and 10w-30 should not preform the same under full operationg temps.

Whats your thoughts?

 

Found this
10W30 is the closest thing to a one size fits all oil. Many older vehicles need 10W30, and most newer vehicles are okay with it in warmer climates. Since many garages don’t want to have multiple tanks of bulk oil they choose to carry only 10W30. The advice that Tom & Ray give is correct, ’it would not be a disaster if you used 10W30, but given a choice, go with the manufacturer’s recommendation and use the 5W30.’Is there a disadvantage to using an oil that flows better when cold, i.e. 5W30 versus 10W30?
Why do many oil change places, even dealerships, use 10W30 instead of 5W30, even when 5W30 is preferred?
According to Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer’s recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.


I hope this helps.

 

That's a really good summary. I would add a couple of things though. If you are willing to experiment, you can pick your oil viscosity based on your normal operating temp oil pressure. The idea is to pick the thinnest oil possible to reduce wear at startup and all the time the oil is getting up to temp, provide adequate oil pressure, and reduce the ratio of viscosity modifiers to base stock for the reasons mentioned above. You might need to look into using synthetic oil and possibly a remote oil cooler to accomplish this, and/or follow recommend oil change intervals. This is not necessaraly an easy question to answer....

This brings up a comon confusion about synthetic oil. Some people believe (as I did years ago when synthetic 1st came out) that synthetic oil is produced in lab by mixing chemicals together under the right conditions to creat a man-made oil so to speak. Synthetic oil is made from crude oil just like the dino oil we as all used to, but the base stock is more highly refined and thus requires less viscosity modifiers. Refer to the post above for a rehash of why you want less viscosity modifiers in your oil.

If you have the interest and some time to dig around, bobistheoilguy.com is a great place to possibly answer your question, or confuse you more.....

 

I have no idea what you are trying to say here? Doesn't make sense at all???
Totally incorrect. Synthetic oil is manmade from Organic esters and synthesized hydrocarbons. Go back to believing what you initially thought. Take a look HERE if you don't believe me.

At any rate, the W is the "winter" viscosity of cold start-ups. The 30 is the viscosity at operating temp. So, 5w-30 covers a wider range of temperatures than 10w-30 does and that is why is is more widely used in todays vehicles than 10w-30. Also, more manufacturers are going to 5w-20 which IS a thinner oil at operating temp than 5w-30.
All-in-all, 5w-30 is a better oil and covers a wider range than 10w-30. You WILL NOT lose with 5w-30 as compared to 10w-30. If the ambient temp is hot, the oil will likely never be as thin as it's rated 5w and will be more like 10w or even 20w depending on how hot out it is. Oil is actually thinner the colder it is outside even though you percieve it as being "thick" to pour when cold and "runny" when hot. Viscosity does not work like that. Don't get confused. I have no idea why there are published books that say otherwise. They clearly have no idea what they are talking about and are speaking from "hearsay" that is totally false.
I'm taking Physics right now and we already covered fluid density, viscosity and pressure. There are many things automakers and oil makers get wrong. it's simply amazing. Like transmission fluid or brake fluid which is pasted on all the bottles. It's not really a fluid, it's actually a liquid. There is a difference.

 

At any rate, the W is the "winter" viscosity of cold start-ups. The 30 is the viscosity at operating temp. So, 5w-30 covers a wider range of temperatures than 10w-30 does and that is why is is more widely used in todays vehicles than 10w-30. Also, more manufacturers are going to 5w-20 which IS a thinner oil at operating temp than 5w-30.
All-in-all, 5w-30 is a better oil and covers a wider range than 10w-30. You WILL NOT lose with 5w-30 as compared to 10w-30. If the ambient temp is hot, the oil will likely never be as thin as it's rated 5w and will be more like 10w or even 20w depending on how hot out it is. Oil is actually thinner the colder it is outside even though you percieve it as being "thick" to pour when cold and "runny" when hot. Viscosity does not work like that. Don't get confused. I have no idea why there are published books that say otherwise. They clearly have no idea what they are talking about and are speaking from "hearsay" that is totally false.
I'm taking Physics right now and we already covered fluid density, viscosity and pressure. There are many things automakers and oil makers get wrong. it's simply amazing. Like transmission fluid or brake fluid which is pasted on all the bottles. It's not really a fluid, it's actually a liquid. There is a difference.[/QUOTE]

I was trying to dance around the complex discussion of motor oil by trying to give a practical example of how to choose the weight of oil, but after re-reading myself, I can see I'm not making sense. I'll table this one for now..


You are correct about synthetic. I guess I got tripped up over the years when they use the term "base stock". It just makes me think of crude, but obviously it is a generic term.

What reference did you pull this from? If this is a case of arguing semantics when referring to the viscosity of multi-weight oil then it would be nice for you to give some more definition, because I don't understand. Otherwise, it's just confusing because the "world" is used to interchanging the terms thickness and viscosity, and viscosity decreases when temperature increases. The oil sitting in the crankcase of my engine does not pour or pump as quickly at 20 deg below then it does at 212....

Once again, I've found that the "world" uses fluid and liquid interchangably, and it just seems to confuse people when you break it down further. What you say is still confusing since liquid is a type of fluid...

It still bugs me sometimes when motor and engine get interchanged, but I'm sure I have done it myself without thinking lot's of times....

 

Dirty Dog has this locked down!!!

I used to think that 10w 30 meant that 30 was the weight it started at and 10 was the weight at operating temp. Course I also thought "W" meant Weight.

Lovin me some 0W-40 in the Dodge.

 

I thought I was losing my marbles for a minute. Thanks for clarifying that up...lol

Sorry about that. I was just trying to say that viscosity simpliy varies inversely with temperature.

Going to a heavier "weight" oil is good for the bottom end, but can be detrimental to the upper end given time. Opposite goes for lighter oil.
Car companies say to use 5w-20. I would never use 5w-20. 5w-30 is what I would reccomend using for every vehicle out there unless you live in Florida or Arizona, then use 10w-30 or a straight up 30.
The fuel savings of 5w-20 or 0w-20 compared to 5w-30 is fractional. Like 0.1mpg which is merely decreasing your long term engine life. Now, it does save a bit when computing 100kmi, but not as much as a reman. engine would cost not even including the labot to install it.

 

[/QUOTE]Car companies say to use 5w-20. I would never use 5w-20. 5w-30 is what I would reccomend using for every vehicle out there unless you live in Florida or Arizona, then use 10w-30 or a straight up 30.
The fuel savings of 5w-20 or 0w-20 compared to 5w-30 is fractional. Like 0.1mpg which is merely decreasing your long term engine life. Now, it does save a bit when computing 100kmi, but not as much as a reman. engine would cost not even including the labot to install it.[/QUOTE]

Question about that. I live in Canada. Right now it is -17C. My manual states I HAVE to use 5W20 because I have MDS. And I am still under warranty. Should I switch now, or wait till my warranty is up?

 

Car companies say to use 5w-20. I would never use 5w-20. 5w-30 is what I would reccomend using for every vehicle out there unless you live in Florida or Arizona, then use 10w-30 or a straight up 30.
The fuel savings of 5w-20 or 0w-20 compared to 5w-30 is fractional. Like 0.1mpg which is merely decreasing your long term engine life. Now, it does save a bit when computing 100kmi, but not as much as a reman. engine would cost not even including the labot to install it.[/quote]

Question about that. I live in Canada. Right now it is -17C. My manual states I HAVE to use 5W20 because I have MDS. And I am still under warranty. Should I switch now, or wait till my warranty is up?[/quote]

My 07 Hemi w/mds throws a MIL if I use 5w-30.
I use only 5w-20 now, no issues.

 

I agree. I think that it was '05 when Dodge switched the oil caps from what it used to be (10w-30 or 5w30) to 5w-20. I believe it was to help with the manditated CAFE standards to increase fuel economy, becuse the engine did not change from '04 to '05! I'd rather pay whatever difference in fuel economy switching to a heavier oil to get longer life out of the engine. I can't speak to what might happen with MDS if you use a different viscosity, but using a heavier oil in the older trucks is the way to go IMHO. 0w-30 sounds like the ticket.....