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Unread 10-27-2013, 03:08 PM   #1
Michaelgoesrawr
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Motor Oil 101?

Being as i'm a young, knowledge thirsty Jeep owner who needs an oil change, I went back to the question "What oil is best for my Jeep?" Well as many of you know, that question brings up other questions. Mainly "What are your driving conditions?".

It's been a well thought of fact that you need different viscosities of motor oil for different temperatures and the condition of your motor.

Well, it's going to be getting colder here, we very rarely see startup conditions that are under 10 degrees fahrenheit, so conventional thinking would be to go with 10-30 motor oil. (I think? I have no idea if that is even a decent way to think of it at this point. Which is why I'm trying to learn).

Well I came across this site http://www.bobistheoilguy.com/motor-oil-101/ that has a bunch of different information about oil viscosities, it has basic information and race geared information. But basically, what I got out of it, is that 10-XX motor oil is too thick for start up in all but 100 degree weather. So my thinking is that my Jeeps (4.2/4.0) would need 0-30 during the winter to reduce start up wear and tear on the motors. Because it will have the lowest viscosity possible when cold but still have the higher viscosity needed at operating temperature. Is that even remotely correct?

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Unread 10-27-2013, 03:59 PM   #2
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Unread 10-27-2013, 04:37 PM   #3
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Originally Posted by Anticanman
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Unread 10-27-2013, 05:00 PM   #4
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10W-40 in the summer and 10W-30 in the winter. Unless you are in the arctic like northern Alaska you will be fine.

Do they even sell 0W-30 where you live? If so try it.

The thinner in the cold helps you start. Because when you try to start cold engines when the crank hits that thick oil it doesn't want to spin fast enough to start.

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Unread 10-27-2013, 05:10 PM   #5
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I run synthetic oil, I usually run Valvoline F/S High Milage on both of my Jeeps with a Wix filter, Unless the K&N filter is on sale
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Unread 10-27-2013, 05:41 PM   #6
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On the OPs engine, you need to run a diesel oil like Rotella 15w-40 or use one of the zinc additives.

I have run Rotella 15W-40 in all my gassers older than 1995, and all my diesel engines. No problems starting anything in cold weather, even when the it is so cold the well head freezes up, and I can't make morning coffee due to no water.
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Unread 10-27-2013, 07:32 PM   #7
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Quote:
Originally Posted by jokerchief462 View Post
10W-40 in the summer and 10W-30 in the winter. Unless you are in the arctic like northern Alaska you will be fine.

Do they even sell 0W-30 where you live? If so try it.

The thinner in the cold helps you start. Because when you try to start cold engines when the crank hits that thick oil it doesn't want to spin fast enough to start.

Sent from underneath my Jeep
Yeah, thats what I gathered from the website.

Quote:
Originally Posted by Tom95YJ View Post
I run synthetic oil, I usually run Valvoline F/S High Milage on both of my Jeeps with a Wix filter, Unless the K&N filter is on sale
According to that website, synthetic is still too thick at start up. But it's 50% better. There were diagrams and things that made it make sense at the time lol.

Quote:
Originally Posted by Old4X View Post
On the OPs engine, you need to run a diesel oil like Rotella 15w-40 or use one of the zinc additives.

I have run Rotella 15W-40 in all my gassers older than 1995, and all my diesel engines. No problems starting anything in cold weather, even when the it is so cold the well head freezes up, and I can't make morning coffee due to no water.
Because our cams and lack of detergents in the gasser oil?

Im still trying to understand the different weights. Key points from the website that I understand are that

-10-xx is too thick for start up at any temperature
- I dont think I need xx-40 because I have the recommended 10psi per 1000 rpms and using it would increase pressure but decrease actual oil flow.

Im just trying to make sense of it all. Lol. Thanks for the replies. I appreciate it.
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Unread 10-27-2013, 07:32 PM   #8
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Quote:
Originally Posted by Old4X
On the OPs engine, you need to run a diesel oil like Rotella 15w-40 or use one of the zinc additives. I have run Rotella 15W-40 in all my gassers older than 1995, and all my diesel engines. No problems starting anything in cold weather, even when the it is so cold the well head freezes up, and I can't make morning coffee due to no water.
You don't need I run diesel in the 4.2l the factory used 10w30.
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Unread 10-27-2013, 08:24 PM   #9
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15w-40 in the summer 10w-40 in the winter

or better yet 5w-40 in the winter if you're not afraid of synthetic
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Unread 10-27-2013, 08:28 PM   #10
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Quote:
Originally Posted by Tom95YJ View Post
You don't need I run diesel in the 4.2l the factory used 10w30.
the factory used 10w-30 back when zinc levels were nice and high and the engine had brand new bearings with tight tolerances

my 4.2 with over 200,000 miles loved 15w-40
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Unread 10-28-2013, 08:46 AM   #11
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I'm running 15W/40 Rotella CJ-4 diesel oil in my 4.2L. The Jeep is doing fine on it, and I'm getting less cold startup lifter clatter than I did on 10W/30 gasser oil.

That makes it nice since it is the same oil I run in my diesel pickup. And other than that convenience, I'm not finicky about oils. For the most part, anything close to factory specs work just fine. Oil is oil. I tend to lean toward a little heavier base stock in high mileage engines.
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Unread 10-28-2013, 11:19 AM   #12
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In theory your right but in the real world it does not matter. 15-40 is fine and will not hurt a thing. Engines heat up the oil extremely fast and the proper viscosity is achieved in a matter of minutes.
Even if you drained all the oil out of an engine there is enough residual oil to keep it lubricated for some time. Diesel and farm machinery all run 15-40 and that is what the 4.0 is equivalent to.
Think about it this way...there has never been any scientific data to prove otherwise so don't lose sleep over what oil to put in the antiquated 4.0. These engines consistently run up 200,000+ miles on all kinds of oil!
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Unread 10-28-2013, 11:29 AM   #13
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Quote:
Originally Posted by jokerchief462 View Post
10W-40 in the summer and 10W-30 in the winter...
Not to pick on you, but why? You realize that the Winter (10W) rating is the same for those two oils? And running temp is the same for your engine in winter or summer. So why change?

If you went with something 0W or 5W in the winter, that would make sense, although not necessary for most of us.
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Unread 10-28-2013, 02:51 PM   #14
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Unread 10-28-2013, 03:57 PM   #15
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Don`t believe everything you read on the internet.
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